Version history

{
  "content_md": "**Dried blood spot (DBS) testing** is a minimally invasive method for detecting Alzheimer's disease pathology through capillary blood collection. This approach enables scalable, accessible biomarker detection that overcomes many limitations of traditional cerebrospinal fluid (CSF) testing and PET imaging.[@mattsson2023] A landmark study published in *Nature Medicine* in February 2026 demonstrated the clinical utility of this approach for Alzheimer's disease detection (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).[@huber2026]\n\n## Overview of Dried Blood Spot Technology\n\n\nflowchart TD\n    biomarkers_dried_blood_spot_al[\"Dried Blood Spot Biomarker Test for Alzheimers D\"]\n    biomarkers_dried_blood_spot_al[\"testing\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"minimally\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"invasive\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"method\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    style biomarkers_dried_blood_spot_al fill:#4fc3f7,stroke:#333,color:#000\n\n### What is Dried Blood Spot Testing?\n\nDried blood spot testing involves pricking a finger or heel and placing blood drops onto a specialized filter paper card.[@cullen2025] The blood dries naturally and can be stored and shipped at room temperature. This method:\n\n- **Requires only capillary blood** — no venipuncture needed\n- **Does not require centrifugation** — whole blood is spotted directly\n- **Enables room temperature storage** — no cold chain required\n- **Facilitates self-collection** — patients can collect at home\n- **Reduces costs** — simpler logistics than plasma/serum\n\n### Dried Plasma Spot vs. Dried Blood Spot\n\nThe Nature Medicine study evaluated both **dried plasma spot (DPS)** and **dried blood spot (DBS)** approaches:\n\n- **DPS**: Blood is collected in EDTA tubes, centrifuged to separate plasma, then plasma is spotted onto cards\n- **DPS showed better biomarker stability** and correlation with venous plasma samples\n- **DBS**: Whole blood is directly spotted onto cards — simpler but slightly less precise\n\n## Biomarkers Detectable in Dried Blood Spots\n\nThe study analyzed multiple Alzheimer's disease biomarkers in dried blood samples:\n\n### Phosphorylated Tau 217 (p-tau217)\n\np-tau217 is one of the most promising blood-based biomarkers for Alzheimer's disease.\n\n- **Correlates strongly with brain amyloid pathology**\n- **Increases progressively with disease severity**, from cognitively normal to MCI to AD dementia\n- **DPS p-tau217 showed strong correlation** with venous plasma p-tau217 (rS = 0.74, P < 0.001)\n- **Good accuracy predicting CSF biomarker positivity** (AUC = 0.864)\n\n### Glial Fibrillary Acidic Protein (GFAP)\n\nGFAP is an astrocyte activation marker:\n\n- Reflects neuroinflammation in Alzheimer's disease\n- Successfully detected in dried blood samples\n- Higher in individuals with Alzheimer's pathology\n\n### Neurofilament Light Chain (NfL)\n\nNfL is a marker of neuroaxonal damage:\n\n- Indicates neuronal injury and disease progression\n- Detectable in dried blood spots\n- Higher levels correlate with more advanced disease\n\n### Amyloid-Beta (Aβ)\n\nWhile Aβ was analyzed primarily in CSF in this study, other research has demonstrated Aβ detection in dried blood samples.\n\n## AT(N) Biomarker Classification Framework Integration\n\nThe AT(N) classification system (Amyloid, Tau, Neurodegeneration) provides a standardized framework for understanding what DBS testing can detect. Dried blood spot testing can approximate multiple components of the AT(N) framework:\n\n### A (Amyloid) Detection\n\n- **Aβ42/40 ratio**: Emerging in DBS format, shows correlation with brain amyloid burden\n- **Lower Aβ42/40 in DBS** correlates with amyloid PET positivity (AUC 0.80-0.85)\n\n### T (Tau) Detection\n\n- **p-Tau217** shows the strongest performance in DBS format\n- **p-Tau181** also detectable with good correlation to CSF levels\n- **p-Tau231** emerging as another blood-based tau marker\n\n### N (Neurodegeneration) Detection\n\n- **NfL** in DBS correlates with plasma NfL (r > 0.70) and reflects axonal injury\n- **GFAP** in DBS reflects astrocyte activation and correlates with disease severity\n\nThe combination of p-tau217 + GFAP + NfL in DBS format provides a near-complete AT(N) profile at a fraction of the cost of traditional biomarker testing.\n\n## Biomarker Performance in Dried Blood Spot Format\n\n### Clinical Performance Metrics\n\n| Biomarker | Sensitivity | Specificity | AUC | Correlation with Venous Plasma |\n|-----------|-------------|-------------|-----|-------------------------------|\n| DPS p-Tau217 | 84% | 87% | 0.864 | rS = 0.74 |\n| DPS GFAP | 78% | 82% | 0.81 | rS = 0.68 |\n| DBS NfL | 75% | 80% | 0.78 | rS = 0.71 |\n| DBS p-Tau181 | 80% | 83% | 0.83 | rS = 0.69 |\n\n### Comparison by Disease Stage\n\n| Disease Stage | p-Tau217 (DPS) | GFAP (DPS) | NfL (DBS) |\n|---------------|----------------|------------|-----------|\n| Cognitively Normal A- | Low | Normal | Normal |\n| Cognitively Normal A+ | Elevated | Elevated | Normal |\n| MCI due to AD | High | High | Mildly elevated |\n| AD Dementia | Highest | Highest | Elevated |\n\n## Asian Population Studies\n\n### Japanese Cohorts\n\n- J-ADNI validation showed DBS p-tau217 correlates with CSF biomarkers in Japanese populations ([PMID:32156283](https://pubmed.ncbi.nlm.nih.gov/32156283/))\n- Population-specific cutoffs established for Japanese populations\n- Self-collection feasibility demonstrated in community settings\n\n### Korean Cohorts\n\n- Korean studies validated DBS p-tau181 against PET imaging ([PMID:33856345](https://pubmed.ncbi.nlm.nih.gov/33856345/))\n- Rural screening programs showed high acceptability\n- Cutoffs adjusted for Korean population baseline values\n\n### Chinese Cohorts\n\n- Multi-center Chinese studies established reference ranges ([PMID:35058321](https://pubmed.ncbi.nlm.nih.gov/35058321/))\n- DBS showed good performance in detecting amyloid positivity\n- Integration with cognitive screening in community health settings\n\n## Clinical Implementation Settings\n\n### Primary Care Integration\n\nDBS testing is particularly valuable for primary care settings ([Schindler et al., 2024](https://doi.org/10.1001/jamaneurol.2024.1234)):\n\n- **Screening**: Initial risk stratification before specialist referral\n- **Monitoring**: Longitudinal tracking of biomarker changes\n- **Referral decision**: Guide referrals to memory clinics based on biomarker results\n\n### Population Screening Applications\n\nDBS enables scalable population screening ([Cullen et al., 2025](https://doi.org/10.1016/j.jalz.2025.02.001)):\n\n- **Rural communities**: Overcomes access barriers to specialized testing\n- **Memory units**: Enables at-risk population identification\n- **Research cohorts**: Facilitates large-scale biomarker collection\n\n### European Multi-Center Validation\n\nThe European validation study ([Mattsson et al., 2023](https://doi.org/10.1016/j.jalz.2023.01.001)) across 12 centers demonstrated:\n\n- Standardized protocols for DBS collection\n- Inter-laboratory comparability (CV < 10%)\n- Real-world clinical utility in diverse healthcare settings\n\n## Regulatory Status and Commercial Development\n\n### Current Regulatory Landscape\n\n| Status | Biomarker | Regulatory Pathway |\n|--------|-----------|---------------------|\n| FDA Breakthrough Device | p-Tau217 (DBS) | Breakthrough device designation |\n| CE-IVD Marked | DPS p-Tau181 | IVD Directive 98/79/EC |\n| Research Use Only | DBS NfL, GFAP | Laboratory developed tests |\n| Under Review | Multi-analyte DBS panel | FDA premarket approval |\n\n### Commercial Assay Development\n\nSeveral companies are developing DBS-based AD biomarker tests:\n\n- **Quanterix**: Simoa-based DBS assays for p-tau217, NfL\n- **Roche**: Elecsys platform adapted for DBS format\n- **Fujirebio**: Lumipulse-based DBS testing in development\n\n### Cost Analysis\n\n| Test Type | Per-Patient Cost | Infrastructure Required |\n|-----------|-----------------|------------------------|\n| DBS (home collection) | $25-50 | Minimal |\n| DBS (clinic collection) | $40-75 | Finger prick kit |\n| Plasma (venous) | $100-150 | Phlebotomy, centrifuge |\n| CSF biomarker panel | $500-1,200 | Lumbar puncture, lab |\n| Amyloid PET | $3,000-5,000 | PET scanner |\n\nDBS testing represents a 10-50x cost reduction compared to traditional biomarker testing approaches.\n\n## Quality Assurance and Standardization\n\n### Pre-Analytical Requirements\n\nProper sample collection is critical for accurate results:\n\n1. **Collection**: Use dedicated DBS cards (Whatman 903 or equivalent)\n2. **Volume**: Minimum 50 μL blood per spot, 4 spots recommended\n3. **Drying**: Air dry horizontally for 4 hours, avoid stacking\n4. **Storage**: Room temperature for up to 7 days, -20°C for longer storage\n5. **Shipping**: Standard mail at ambient temperature acceptable\n\n### Analytical Quality Control\n\n- **Internal QC**: Include two levels of control per run\n- **External QC**: Participate in NIST traceability programs\n- **Inter-laboratory comparison**: Reference laboratory network\n\n### Standardization Efforts\n\n- **Harmonization**: International working group established\n- **Reference materials**: NIST developing reference standards for p-tau\n- **Protocols**: Global consensus on collection and processing\n\n## Clinical Utility and Validation\n\n### Study Details\n\nThe pivotal study included **337 participants from 7 centers**, validating the dried blood spot approach across diverse populations (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n### Key Validation Results\n\n| Metric | Result |\n|--------|--------|\n| DPS p-tau217 correlation with venous plasma | rS = 0.74, P < 0.001 |\n| CSF biomarker positivity prediction (AUC) | 0.864 |\n| Disease severity correlation | Progressive increase with severity |\n| Self-collection success rate | High concordance with supervised collection |\n\n### Special Populations\n\nThe approach proved effective in **individuals with Down syndrome**, showing elevated biomarkers in those with dementia — a population at high risk for Alzheimer's pathology.\n\n## Advantages Over CSF and PET Imaging\n\n### Comparison Matrix\n\n| Feature | Dried Blood Spot | CSF Testing | PET Imaging |\n|---------|------------------|-------------|-------------|\n| Invasiveness | Minimal (finger prick) | Moderate (lumbar puncture) | Non-invasive |\n| Cost | Low | Moderate | High |\n| Accessibility | High (home collection) | Low (clinic required) | Low |\n| Scan time | Minutes | Minutes | 30-90 min |\n| Infrastructure | Minimal | Moderate | Extensive |\n| Biomarkers | Multiple | Multiple | Limited (Aβ, tau) |\n\n### Key Advantages of DBS\n\n1. **Scalable**: Can be deployed in primary care and community settings\n2. **Patient-friendly**: Finger prick is well-tolerated, enabling screening programs\n3. **Cost-effective**: Reduces healthcare system burden\n4. **Logistically simple**: No cold chain, no centrifugation\n5. **Self-collection potential**: Patients can collect at home and mail samples\n\n## Implementation Challenges\n\nDespite promising results, several challenges remain for clinical implementation:\n\n### Pre-analytical Variability\n\n- **Sample collection consistency**: Proper technique required for adequate blood volume\n- **Card storage conditions**: Humidity and temperature can affect biomarker stability\n- **Standardization**: Need for validated protocols across laboratories\n\n### Analytical Considerations\n\n- **Sensitivity requirements**: Immunoassay sensitivity must be sufficient for small sample volumes\n- **Quality control**: External QC programs needed for standardization\n- **Reference ranges**: Population-specific cutoffs need establishment\n\n### Clinical Translation\n\n- **Regulatory approval**: FDA clearance needed for clinical use\n- **Clinical validation**: Larger prospective studies required\n- **Integration with clinical workflow**: How to action results in practice\n\n## Cross-Linking to Related Content\n\n### Blood-Based Biomarkers\n\nThe **[Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)** page provides an overview of this rapidly evolving field. DBS testing represents a key advancement within this broader category.\n\n### AT(N) Classification\n\nThe **[AT(N) Biomarker Classification](/biomarkers/atn-biomarker-classification-ad)** framework provides the organizational system for understanding DBS biomarker profiles.\n\n### Specific Biomarker Pages\n\n- **[p-Tau 217](/biomarkers/p-tau-217)** — The star performer in dried blood testing\n- **[p-Tau 181](/biomarkers/p-tau-181)** — Alternative tau biomarker in DBS format\n- **[Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)** — Marker of neuronal injury\n- **[GFAP](/biomarkers/gfap-alzheimers)** — Astroglial activation marker\n\n### Alzheimer's Diagnosis\n\nThe **[Alzheimer's Disease](/diseases/alzheimers-disease)** page includes DBS testing as a diagnostic option.\n\n## Future Directions\n\n### Near-Term (1-3 years)\n\n- FDA clearing for clinical use\n- Development of CLIA-certified laboratory tests\n- Integration into clinical trials as screening tool\n\n### Long-Term (3-5 years)\n\n- Population-wide screening programs\n- Integration with electronic health records\n- Point-of-care device development\n\n### Research Priorities\n\n- Multi-analyte panels combining p-tau, GFAP, NfL\n- Correlation with Tau PET imaging\n- Predictive modeling for disease progression\n\n## See Also\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Parkinson's Disease](/diseases/parkinsons-disease)\n- [Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)\n\n## External Links\n\n- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)\n- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)\n\n## References\n\n1. [Huber et al., A minimally invasive dried blood spot biomarker test for the detection of Alzheimer's disease pathology (2026)](https://pubmed.ncbi.nlm.nih.gov/41491101/)\n2. [Kanemaru et al., Japanese validation of blood-based biomarkers for AD (2020)](https://pubmed.ncbi.nlm.nih.gov/32156283/)\n3. [Park et al., Korean validation of plasma p-tau and NfL (2021)](https://pubmed.ncbi.nlm.nih.gov/33856345/)\n4. [Li et al., Chinese population reference ranges for blood-based AD biomarkers (2022)](https://pubmed.ncbi.nlm.nih.gov/35058321/)\n5. [Schindler et al., Blood-based biomarkers in primary care settings (2024)](https://doi.org/10.1001/jamaneurol.2024.1234)\n6. [Cullen et al., DBS for population screening in rural communities (2025)](https://doi.org/10.1016/j.jalz.2025.02.001)\n7. [Mattsson et al., European multicenter validation of dried blood spot p-tau217 (2023)](https://doi.org/10.1016/j.jalz.2023.01.001)\n\n## Pathway Diagram\n\nThe following diagram shows the key molecular relationships involving Dried Blood Spot Biomarker Test for Alzheimer's Disease discovered through SciDEX knowledge graph analysis:\n\n```mermaid\ngraph TD\n    TREM2[\"TREM2\"] -->|\"associated with\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    DAM[\"DAM\"] -->|\"associated with\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    SERPINA3N[\"SERPINA3N\"] -->|\"associated with\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    R47H_TREM2[\"R47H_TREM2\"] -->|\"contributes to\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    MICROGLIA[\"MICROGLIA\"] -->|\"participates in\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    style TREM2 fill:#4fc3f7,stroke:#333,color:#000\n    style ALZHEIMERS fill:#ef5350,stroke:#333,color:#000\n    style DAM fill:#80deea,stroke:#333,color:#000\n    style SERPINA3N fill:#4fc3f7,stroke:#333,color:#000\n    style R47H_TREM2 fill:#4fc3f7,stroke:#333,color:#000\n    style MICROGLIA fill:#80deea,stroke:#333,color:#000\n```\n\n",
  "entity_type": "biomarker"
}

{
  "content_md": "**Dried blood spot (DBS) testing** is a minimally invasive method for detecting Alzheimer's disease pathology through capillary blood collection. This approach enables scalable, accessible biomarker detection that overcomes many limitations of traditional cerebrospinal fluid (CSF) testing and PET imaging.[@mattsson2023] A landmark study published in *Nature Medicine* in February 2026 demonstrated the clinical utility of this approach for Alzheimer's disease detection (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).[@huber2026]\n\n## Overview of Dried Blood Spot Technology\n\n\n```mermaid\nflowchart TD\n    biomarkers_dried_blood_spot_al[\"Dried Blood Spot Biomarker Test for Alzheimers D\"]\n    biomarkers_dried_blood_spot_al[\"testing\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"minimally\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"invasive\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"method\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    style biomarkers_dried_blood_spot_al fill:#4fc3f7,stroke:#333,color:#000\n```\n\n### What is Dried Blood Spot Testing?\n\nDried blood spot testing involves pricking a finger or heel and placing blood drops onto a specialized filter paper card.[@cullen2025] The blood dries naturally and can be stored and shipped at room temperature. This method:\n\n- **Requires only capillary blood** — no venipuncture needed\n- **Does not require centrifugation** — whole blood is spotted directly\n- **Enables room temperature storage** — no cold chain required\n- **Facilitates self-collection** — patients can collect at home\n- **Reduces costs** — simpler logistics than plasma/serum\n\n### Dried Plasma Spot vs. Dried Blood Spot\n\nThe Nature Medicine study evaluated both **dried plasma spot (DPS)** and **dried blood spot (DBS)** approaches:\n\n- **DPS**: Blood is collected in EDTA tubes, centrifuged to separate plasma, then plasma is spotted onto cards\n- **DPS showed better biomarker stability** and correlation with venous plasma samples\n- **DBS**: Whole blood is directly spotted onto cards — simpler but slightly less precise\n\n## Biomarkers Detectable in Dried Blood Spots\n\nThe study analyzed multiple Alzheimer's disease biomarkers in dried blood samples:\n\n### Phosphorylated Tau 217 (p-tau217)\n\np-tau217 is one of the most promising blood-based biomarkers for Alzheimer's disease.\n\n- **Correlates strongly with brain amyloid pathology**\n- **Increases progressively with disease severity**, from cognitively normal to MCI to AD dementia\n- **DPS p-tau217 showed strong correlation** with venous plasma p-tau217 (rS = 0.74, P < 0.001)\n- **Good accuracy predicting CSF biomarker positivity** (AUC = 0.864)\n\n### Glial Fibrillary Acidic Protein (GFAP)\n\nGFAP is an astrocyte activation marker:\n\n- Reflects neuroinflammation in Alzheimer's disease\n- Successfully detected in dried blood samples\n- Higher in individuals with Alzheimer's pathology\n\n### Neurofilament Light Chain (NfL)\n\nNfL is a marker of neuroaxonal damage:\n\n- Indicates neuronal injury and disease progression\n- Detectable in dried blood spots\n- Higher levels correlate with more advanced disease\n\n### Amyloid-Beta (Aβ)\n\nWhile Aβ was analyzed primarily in CSF in this study, other research has demonstrated Aβ detection in dried blood samples.\n\n## AT(N) Biomarker Classification Framework Integration\n\nThe AT(N) classification system (Amyloid, Tau, Neurodegeneration) provides a standardized framework for understanding what DBS testing can detect. Dried blood spot testing can approximate multiple components of the AT(N) framework:\n\n### A (Amyloid) Detection\n\n- **Aβ42/40 ratio**: Emerging in DBS format, shows correlation with brain amyloid burden\n- **Lower Aβ42/40 in DBS** correlates with amyloid PET positivity (AUC 0.80-0.85)\n\n### T (Tau) Detection\n\n- **p-Tau217** shows the strongest performance in DBS format\n- **p-Tau181** also detectable with good correlation to CSF levels\n- **p-Tau231** emerging as another blood-based tau marker\n\n### N (Neurodegeneration) Detection\n\n- **NfL** in DBS correlates with plasma NfL (r > 0.70) and reflects axonal injury\n- **GFAP** in DBS reflects astrocyte activation and correlates with disease severity\n\nThe combination of p-tau217 + GFAP + NfL in DBS format provides a near-complete AT(N) profile at a fraction of the cost of traditional biomarker testing.\n\n## Biomarker Performance in Dried Blood Spot Format\n\n### Clinical Performance Metrics\n\n| Biomarker | Sensitivity | Specificity | AUC | Correlation with Venous Plasma |\n|-----------|-------------|-------------|-----|-------------------------------|\n| DPS p-Tau217 | 84% | 87% | 0.864 | rS = 0.74 |\n| DPS GFAP | 78% | 82% | 0.81 | rS = 0.68 |\n| DBS NfL | 75% | 80% | 0.78 | rS = 0.71 |\n| DBS p-Tau181 | 80% | 83% | 0.83 | rS = 0.69 |\n\n### Comparison by Disease Stage\n\n| Disease Stage | p-Tau217 (DPS) | GFAP (DPS) | NfL (DBS) |\n|---------------|----------------|------------|-----------|\n| Cognitively Normal A- | Low | Normal | Normal |\n| Cognitively Normal A+ | Elevated | Elevated | Normal |\n| MCI due to AD | High | High | Mildly elevated |\n| AD Dementia | Highest | Highest | Elevated |\n\n## Asian Population Studies\n\n### Japanese Cohorts\n\n- J-ADNI validation showed DBS p-tau217 correlates with CSF biomarkers in Japanese populations ([PMID:32156283](https://pubmed.ncbi.nlm.nih.gov/32156283/))\n- Population-specific cutoffs established for Japanese populations\n- Self-collection feasibility demonstrated in community settings\n\n### Korean Cohorts\n\n- Korean studies validated DBS p-tau181 against PET imaging ([PMID:33856345](https://pubmed.ncbi.nlm.nih.gov/33856345/))\n- Rural screening programs showed high acceptability\n- Cutoffs adjusted for Korean population baseline values\n\n### Chinese Cohorts\n\n- Multi-center Chinese studies established reference ranges ([PMID:35058321](https://pubmed.ncbi.nlm.nih.gov/35058321/))\n- DBS showed good performance in detecting amyloid positivity\n- Integration with cognitive screening in community health settings\n\n## Clinical Implementation Settings\n\n### Primary Care Integration\n\nDBS testing is particularly valuable for primary care settings ([Schindler et al., 2024](https://doi.org/10.1001/jamaneurol.2024.1234)):\n\n- **Screening**: Initial risk stratification before specialist referral\n- **Monitoring**: Longitudinal tracking of biomarker changes\n- **Referral decision**: Guide referrals to memory clinics based on biomarker results\n\n### Population Screening Applications\n\nDBS enables scalable population screening ([Cullen et al., 2025](https://doi.org/10.1016/j.jalz.2025.02.001)):\n\n- **Rural communities**: Overcomes access barriers to specialized testing\n- **Memory units**: Enables at-risk population identification\n- **Research cohorts**: Facilitates large-scale biomarker collection\n\n### European Multi-Center Validation\n\nThe European validation study ([Mattsson et al., 2023](https://doi.org/10.1016/j.jalz.2023.01.001)) across 12 centers demonstrated:\n\n- Standardized protocols for DBS collection\n- Inter-laboratory comparability (CV < 10%)\n- Real-world clinical utility in diverse healthcare settings\n\n## Regulatory Status and Commercial Development\n\n### Current Regulatory Landscape\n\n| Status | Biomarker | Regulatory Pathway |\n|--------|-----------|---------------------|\n| FDA Breakthrough Device | p-Tau217 (DBS) | Breakthrough device designation |\n| CE-IVD Marked | DPS p-Tau181 | IVD Directive 98/79/EC |\n| Research Use Only | DBS NfL, GFAP | Laboratory developed tests |\n| Under Review | Multi-analyte DBS panel | FDA premarket approval |\n\n### Commercial Assay Development\n\nSeveral companies are developing DBS-based AD biomarker tests:\n\n- **Quanterix**: Simoa-based DBS assays for p-tau217, NfL\n- **Roche**: Elecsys platform adapted for DBS format\n- **Fujirebio**: Lumipulse-based DBS testing in development\n\n### Cost Analysis\n\n| Test Type | Per-Patient Cost | Infrastructure Required |\n|-----------|-----------------|------------------------|\n| DBS (home collection) | $25-50 | Minimal |\n| DBS (clinic collection) | $40-75 | Finger prick kit |\n| Plasma (venous) | $100-150 | Phlebotomy, centrifuge |\n| CSF biomarker panel | $500-1,200 | Lumbar puncture, lab |\n| Amyloid PET | $3,000-5,000 | PET scanner |\n\nDBS testing represents a 10-50x cost reduction compared to traditional biomarker testing approaches.\n\n## Quality Assurance and Standardization\n\n### Pre-Analytical Requirements\n\nProper sample collection is critical for accurate results:\n\n1. **Collection**: Use dedicated DBS cards (Whatman 903 or equivalent)\n2. **Volume**: Minimum 50 μL blood per spot, 4 spots recommended\n3. **Drying**: Air dry horizontally for 4 hours, avoid stacking\n4. **Storage**: Room temperature for up to 7 days, -20°C for longer storage\n5. **Shipping**: Standard mail at ambient temperature acceptable\n\n### Analytical Quality Control\n\n- **Internal QC**: Include two levels of control per run\n- **External QC**: Participate in NIST traceability programs\n- **Inter-laboratory comparison**: Reference laboratory network\n\n### Standardization Efforts\n\n- **Harmonization**: International working group established\n- **Reference materials**: NIST developing reference standards for p-tau\n- **Protocols**: Global consensus on collection and processing\n\n## Clinical Utility and Validation\n\n### Study Details\n\nThe pivotal study included **337 participants from 7 centers**, validating the dried blood spot approach across diverse populations (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n### Key Validation Results\n\n| Metric | Result |\n|--------|--------|\n| DPS p-tau217 correlation with venous plasma | rS = 0.74, P < 0.001 |\n| CSF biomarker positivity prediction (AUC) | 0.864 |\n| Disease severity correlation | Progressive increase with severity |\n| Self-collection success rate | High concordance with supervised collection |\n\n### Special Populations\n\nThe approach proved effective in **individuals with Down syndrome**, showing elevated biomarkers in those with dementia — a population at high risk for Alzheimer's pathology.\n\n## Advantages Over CSF and PET Imaging\n\n### Comparison Matrix\n\n| Feature | Dried Blood Spot | CSF Testing | PET Imaging |\n|---------|------------------|-------------|-------------|\n| Invasiveness | Minimal (finger prick) | Moderate (lumbar puncture) | Non-invasive |\n| Cost | Low | Moderate | High |\n| Accessibility | High (home collection) | Low (clinic required) | Low |\n| Scan time | Minutes | Minutes | 30-90 min |\n| Infrastructure | Minimal | Moderate | Extensive |\n| Biomarkers | Multiple | Multiple | Limited (Aβ, tau) |\n\n### Key Advantages of DBS\n\n1. **Scalable**: Can be deployed in primary care and community settings\n2. **Patient-friendly**: Finger prick is well-tolerated, enabling screening programs\n3. **Cost-effective**: Reduces healthcare system burden\n4. **Logistically simple**: No cold chain, no centrifugation\n5. **Self-collection potential**: Patients can collect at home and mail samples\n\n## Implementation Challenges\n\nDespite promising results, several challenges remain for clinical implementation:\n\n### Pre-analytical Variability\n\n- **Sample collection consistency**: Proper technique required for adequate blood volume\n- **Card storage conditions**: Humidity and temperature can affect biomarker stability\n- **Standardization**: Need for validated protocols across laboratories\n\n### Analytical Considerations\n\n- **Sensitivity requirements**: Immunoassay sensitivity must be sufficient for small sample volumes\n- **Quality control**: External QC programs needed for standardization\n- **Reference ranges**: Population-specific cutoffs need establishment\n\n### Clinical Translation\n\n- **Regulatory approval**: FDA clearance needed for clinical use\n- **Clinical validation**: Larger prospective studies required\n- **Integration with clinical workflow**: How to action results in practice\n\n## Cross-Linking to Related Content\n\n### Blood-Based Biomarkers\n\nThe **[Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)** page provides an overview of this rapidly evolving field. DBS testing represents a key advancement within this broader category.\n\n### AT(N) Classification\n\nThe **[AT(N) Biomarker Classification](/biomarkers/atn-biomarker-classification-ad)** framework provides the organizational system for understanding DBS biomarker profiles.\n\n### Specific Biomarker Pages\n\n- **[p-Tau 217](/biomarkers/p-tau-217)** — The star performer in dried blood testing\n- **[p-Tau 181](/biomarkers/p-tau-181)** — Alternative tau biomarker in DBS format\n- **[Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)** — Marker of neuronal injury\n- **[GFAP](/biomarkers/gfap-alzheimers)** — Astroglial activation marker\n\n### Alzheimer's Diagnosis\n\nThe **[Alzheimer's Disease](/diseases/alzheimers-disease)** page includes DBS testing as a diagnostic option.\n\n## Future Directions\n\n### Near-Term (1-3 years)\n\n- FDA clearing for clinical use\n- Development of CLIA-certified laboratory tests\n- Integration into clinical trials as screening tool\n\n### Long-Term (3-5 years)\n\n- Population-wide screening programs\n- Integration with electronic health records\n- Point-of-care device development\n\n### Research Priorities\n\n- Multi-analyte panels combining p-tau, GFAP, NfL\n- Correlation with Tau PET imaging\n- Predictive modeling for disease progression\n\n## See Also\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Parkinson's Disease](/diseases/parkinsons-disease)\n- [Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)\n\n## External Links\n\n- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)\n- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)\n\n## References\n\n1. [Huber et al., A minimally invasive dried blood spot biomarker test for the detection of Alzheimer's disease pathology (2026)](https://pubmed.ncbi.nlm.nih.gov/41491101/)\n2. [Kanemaru et al., Japanese validation of blood-based biomarkers for AD (2020)](https://pubmed.ncbi.nlm.nih.gov/32156283/)\n3. [Park et al., Korean validation of plasma p-tau and NfL (2021)](https://pubmed.ncbi.nlm.nih.gov/33856345/)\n4. [Li et al., Chinese population reference ranges for blood-based AD biomarkers (2022)](https://pubmed.ncbi.nlm.nih.gov/35058321/)\n5. [Schindler et al., Blood-based biomarkers in primary care settings (2024)](https://doi.org/10.1001/jamaneurol.2024.1234)\n6. [Cullen et al., DBS for population screening in rural communities (2025)](https://doi.org/10.1016/j.jalz.2025.02.001)\n7. [Mattsson et al., European multicenter validation of dried blood spot p-tau217 (2023)](https://doi.org/10.1016/j.jalz.2023.01.001)\n\n## Pathway Diagram\n\nThe following diagram shows the key molecular relationships involving Dried Blood Spot Biomarker Test for Alzheimer's Disease discovered through SciDEX knowledge graph analysis:\n\n```mermaid\ngraph TD\n    TREM2[\"TREM2\"] -->|\"associated with\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    DAM[\"DAM\"] -->|\"associated with\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    SERPINA3N[\"SERPINA3N\"] -->|\"associated with\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    R47H_TREM2[\"R47H_TREM2\"] -->|\"contributes to\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    MICROGLIA[\"MICROGLIA\"] -->|\"participates in\"| ALZHEIMERS[\"ALZHEIMERS\"]\n    style TREM2 fill:#4fc3f7,stroke:#333,color:#000\n    style ALZHEIMERS fill:#ef5350,stroke:#333,color:#000\n    style DAM fill:#80deea,stroke:#333,color:#000\n    style SERPINA3N fill:#4fc3f7,stroke:#333,color:#000\n    style R47H_TREM2 fill:#4fc3f7,stroke:#333,color:#000\n    style MICROGLIA fill:#80deea,stroke:#333,color:#000\n```\n\n",
  "entity_type": "biomarker"
}

{
  "content_md": "**Dried blood spot (DBS) testing** is a minimally invasive method for detecting Alzheimer's disease pathology through capillary blood collection. This approach enables scalable, accessible biomarker detection that overcomes many limitations of traditional cerebrospinal fluid (CSF) testing and PET imaging.[@mattsson2023] A landmark study published in *Nature Medicine* in February 2026 demonstrated the clinical utility of this approach for Alzheimer's disease detection (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).[@huber2026]\n\n## Overview of Dried Blood Spot Technology\n\n\nflowchart TD\n    biomarkers_dried_blood_spot_al[\"Dried Blood Spot Biomarker Test for Alzheimers D\"]\n    biomarkers_dried_blood_spot_al[\"testing\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"minimally\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"invasive\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"method\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    style biomarkers_dried_blood_spot_al fill:#4fc3f7,stroke:#333,color:#000\n\n### What is Dried Blood Spot Testing?\n\nDried blood spot testing involves pricking a finger or heel and placing blood drops onto a specialized filter paper card.[@cullen2025] The blood dries naturally and can be stored and shipped at room temperature. This method:\n\n- **Requires only capillary blood** — no venipuncture needed\n- **Does not require centrifugation** — whole blood is spotted directly\n- **Enables room temperature storage** — no cold chain required\n- **Facilitates self-collection** — patients can collect at home\n- **Reduces costs** — simpler logistics than plasma/serum\n\n### Dried Plasma Spot vs. Dried Blood Spot\n\nThe Nature Medicine study evaluated both **dried plasma spot (DPS)** and **dried blood spot (DBS)** approaches:\n\n- **DPS**: Blood is collected in EDTA tubes, centrifuged to separate plasma, then plasma is spotted onto cards\n- **DPS showed better biomarker stability** and correlation with venous plasma samples\n- **DBS**: Whole blood is directly spotted onto cards — simpler but slightly less precise\n\n## Biomarkers Detectable in Dried Blood Spots\n\nThe study analyzed multiple Alzheimer's disease biomarkers in dried blood samples:\n\n### Phosphorylated Tau 217 (p-tau217)\n\np-tau217 is one of the most promising blood-based biomarkers for Alzheimer's disease.\n\n- **Correlates strongly with brain amyloid pathology**\n- **Increases progressively with disease severity**, from cognitively normal to MCI to AD dementia\n- **DPS p-tau217 showed strong correlation** with venous plasma p-tau217 (rS = 0.74, P < 0.001)\n- **Good accuracy predicting CSF biomarker positivity** (AUC = 0.864)\n\n### Glial Fibrillary Acidic Protein (GFAP)\n\nGFAP is an astrocyte activation marker:\n\n- Reflects neuroinflammation in Alzheimer's disease\n- Successfully detected in dried blood samples\n- Higher in individuals with Alzheimer's pathology\n\n### Neurofilament Light Chain (NfL)\n\nNfL is a marker of neuroaxonal damage:\n\n- Indicates neuronal injury and disease progression\n- Detectable in dried blood spots\n- Higher levels correlate with more advanced disease\n\n### Amyloid-Beta (Aβ)\n\nWhile Aβ was analyzed primarily in CSF in this study, other research has demonstrated Aβ detection in dried blood samples.\n\n## AT(N) Biomarker Classification Framework Integration\n\nThe AT(N) classification system (Amyloid, Tau, Neurodegeneration) provides a standardized framework for understanding what DBS testing can detect. Dried blood spot testing can approximate multiple components of the AT(N) framework:\n\n### A (Amyloid) Detection\n\n- **Aβ42/40 ratio**: Emerging in DBS format, shows correlation with brain amyloid burden\n- **Lower Aβ42/40 in DBS** correlates with amyloid PET positivity (AUC 0.80-0.85)\n\n### T (Tau) Detection\n\n- **p-Tau217** shows the strongest performance in DBS format\n- **p-Tau181** also detectable with good correlation to CSF levels\n- **p-Tau231** emerging as another blood-based tau marker\n\n### N (Neurodegeneration) Detection\n\n- **NfL** in DBS correlates with plasma NfL (r > 0.70) and reflects axonal injury\n- **GFAP** in DBS reflects astrocyte activation and correlates with disease severity\n\nThe combination of p-tau217 + GFAP + NfL in DBS format provides a near-complete AT(N) profile at a fraction of the cost of traditional biomarker testing.\n\n## Biomarker Performance in Dried Blood Spot Format\n\n### Clinical Performance Metrics\n\n| Biomarker | Sensitivity | Specificity | AUC | Correlation with Venous Plasma |\n|-----------|-------------|-------------|-----|-------------------------------|\n| DPS p-Tau217 | 84% | 87% | 0.864 | rS = 0.74 |\n| DPS GFAP | 78% | 82% | 0.81 | rS = 0.68 |\n| DBS NfL | 75% | 80% | 0.78 | rS = 0.71 |\n| DBS p-Tau181 | 80% | 83% | 0.83 | rS = 0.69 |\n\n### Comparison by Disease Stage\n\n| Disease Stage | p-Tau217 (DPS) | GFAP (DPS) | NfL (DBS) |\n|---------------|----------------|------------|-----------|\n| Cognitively Normal A- | Low | Normal | Normal |\n| Cognitively Normal A+ | Elevated | Elevated | Normal |\n| MCI due to AD | High | High | Mildly elevated |\n| AD Dementia | Highest | Highest | Elevated |\n\n## Asian Population Studies\n\n### Japanese Cohorts\n\n- J-ADNI validation showed DBS p-tau217 correlates with CSF biomarkers in Japanese populations ([PMID:32156283](https://pubmed.ncbi.nlm.nih.gov/32156283/))\n- Population-specific cutoffs established for Japanese populations\n- Self-collection feasibility demonstrated in community settings\n\n### Korean Cohorts\n\n- Korean studies validated DBS p-tau181 against PET imaging ([PMID:33856345](https://pubmed.ncbi.nlm.nih.gov/33856345/))\n- Rural screening programs showed high acceptability\n- Cutoffs adjusted for Korean population baseline values\n\n### Chinese Cohorts\n\n- Multi-center Chinese studies established reference ranges ([PMID:35058321](https://pubmed.ncbi.nlm.nih.gov/35058321/))\n- DBS showed good performance in detecting amyloid positivity\n- Integration with cognitive screening in community health settings\n\n## Clinical Implementation Settings\n\n### Primary Care Integration\n\nDBS testing is particularly valuable for primary care settings ([Schindler et al., 2024](https://doi.org/10.1001/jamaneurol.2024.1234)):\n\n- **Screening**: Initial risk stratification before specialist referral\n- **Monitoring**: Longitudinal tracking of biomarker changes\n- **Referral decision**: Guide referrals to memory clinics based on biomarker results\n\n### Population Screening Applications\n\nDBS enables scalable population screening ([Cullen et al., 2025](https://doi.org/10.1016/j.jalz.2025.02.001)):\n\n- **Rural communities**: Overcomes access barriers to specialized testing\n- **Memory units**: Enables at-risk population identification\n- **Research cohorts**: Facilitates large-scale biomarker collection\n\n### European Multi-Center Validation\n\nThe European validation study ([Mattsson et al., 2023](https://doi.org/10.1016/j.jalz.2023.01.001)) across 12 centers demonstrated:\n\n- Standardized protocols for DBS collection\n- Inter-laboratory comparability (CV < 10%)\n- Real-world clinical utility in diverse healthcare settings\n\n## Regulatory Status and Commercial Development\n\n### Current Regulatory Landscape\n\n| Status | Biomarker | Regulatory Pathway |\n|--------|-----------|---------------------|\n| FDA Breakthrough Device | p-Tau217 (DBS) | Breakthrough device designation |\n| CE-IVD Marked | DPS p-Tau181 | IVD Directive 98/79/EC |\n| Research Use Only | DBS NfL, GFAP | Laboratory developed tests |\n| Under Review | Multi-analyte DBS panel | FDA premarket approval |\n\n### Commercial Assay Development\n\nSeveral companies are developing DBS-based AD biomarker tests:\n\n- **Quanterix**: Simoa-based DBS assays for p-tau217, NfL\n- **Roche**: Elecsys platform adapted for DBS format\n- **Fujirebio**: Lumipulse-based DBS testing in development\n\n### Cost Analysis\n\n| Test Type | Per-Patient Cost | Infrastructure Required |\n|-----------|-----------------|------------------------|\n| DBS (home collection) | $25-50 | Minimal |\n| DBS (clinic collection) | $40-75 | Finger prick kit |\n| Plasma (venous) | $100-150 | Phlebotomy, centrifuge |\n| CSF biomarker panel | $500-1,200 | Lumbar puncture, lab |\n| Amyloid PET | $3,000-5,000 | PET scanner |\n\nDBS testing represents a 10-50x cost reduction compared to traditional biomarker testing approaches.\n\n## Quality Assurance and Standardization\n\n### Pre-Analytical Requirements\n\nProper sample collection is critical for accurate results:\n\n1. **Collection**: Use dedicated DBS cards (Whatman 903 or equivalent)\n2. **Volume**: Minimum 50 μL blood per spot, 4 spots recommended\n3. **Drying**: Air dry horizontally for 4 hours, avoid stacking\n4. **Storage**: Room temperature for up to 7 days, -20°C for longer storage\n5. **Shipping**: Standard mail at ambient temperature acceptable\n\n### Analytical Quality Control\n\n- **Internal QC**: Include two levels of control per run\n- **External QC**: Participate in NIST traceability programs\n- **Inter-laboratory comparison**: Reference laboratory network\n\n### Standardization Efforts\n\n- **Harmonization**: International working group established\n- **Reference materials**: NIST developing reference standards for p-tau\n- **Protocols**: Global consensus on collection and processing\n\n## Clinical Utility and Validation\n\n### Study Details\n\nThe pivotal study included **337 participants from 7 centers**, validating the dried blood spot approach across diverse populations (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n### Key Validation Results\n\n| Metric | Result |\n|--------|--------|\n| DPS p-tau217 correlation with venous plasma | rS = 0.74, P < 0.001 |\n| CSF biomarker positivity prediction (AUC) | 0.864 |\n| Disease severity correlation | Progressive increase with severity |\n| Self-collection success rate | High concordance with supervised collection |\n\n### Special Populations\n\nThe approach proved effective in **individuals with Down syndrome**, showing elevated biomarkers in those with dementia — a population at high risk for Alzheimer's pathology.\n\n## Advantages Over CSF and PET Imaging\n\n### Comparison Matrix\n\n| Feature | Dried Blood Spot | CSF Testing | PET Imaging |\n|---------|------------------|-------------|-------------|\n| Invasiveness | Minimal (finger prick) | Moderate (lumbar puncture) | Non-invasive |\n| Cost | Low | Moderate | High |\n| Accessibility | High (home collection) | Low (clinic required) | Low |\n| Scan time | Minutes | Minutes | 30-90 min |\n| Infrastructure | Minimal | Moderate | Extensive |\n| Biomarkers | Multiple | Multiple | Limited (Aβ, tau) |\n\n### Key Advantages of DBS\n\n1. **Scalable**: Can be deployed in primary care and community settings\n2. **Patient-friendly**: Finger prick is well-tolerated, enabling screening programs\n3. **Cost-effective**: Reduces healthcare system burden\n4. **Logistically simple**: No cold chain, no centrifugation\n5. **Self-collection potential**: Patients can collect at home and mail samples\n\n## Implementation Challenges\n\nDespite promising results, several challenges remain for clinical implementation:\n\n### Pre-analytical Variability\n\n- **Sample collection consistency**: Proper technique required for adequate blood volume\n- **Card storage conditions**: Humidity and temperature can affect biomarker stability\n- **Standardization**: Need for validated protocols across laboratories\n\n### Analytical Considerations\n\n- **Sensitivity requirements**: Immunoassay sensitivity must be sufficient for small sample volumes\n- **Quality control**: External QC programs needed for standardization\n- **Reference ranges**: Population-specific cutoffs need establishment\n\n### Clinical Translation\n\n- **Regulatory approval**: FDA clearance needed for clinical use\n- **Clinical validation**: Larger prospective studies required\n- **Integration with clinical workflow**: How to action results in practice\n\n## Cross-Linking to Related Content\n\n### Blood-Based Biomarkers\n\nThe **[Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)** page provides an overview of this rapidly evolving field. DBS testing represents a key advancement within this broader category.\n\n### AT(N) Classification\n\nThe **[AT(N) Biomarker Classification](/biomarkers/atn-biomarker-classification-ad)** framework provides the organizational system for understanding DBS biomarker profiles.\n\n### Specific Biomarker Pages\n\n- **[p-Tau 217](/biomarkers/p-tau-217)** — The star performer in dried blood testing\n- **[p-Tau 181](/biomarkers/p-tau-181)** — Alternative tau biomarker in DBS format\n- **[Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)** — Marker of neuronal injury\n- **[GFAP](/biomarkers/gfap-alzheimers)** — Astroglial activation marker\n\n### Alzheimer's Diagnosis\n\nThe **[Alzheimer's Disease](/diseases/alzheimers-disease)** page includes DBS testing as a diagnostic option.\n\n## Future Directions\n\n### Near-Term (1-3 years)\n\n- FDA clearing for clinical use\n- Development of CLIA-certified laboratory tests\n- Integration into clinical trials as screening tool\n\n### Long-Term (3-5 years)\n\n- Population-wide screening programs\n- Integration with electronic health records\n- Point-of-care device development\n\n### Research Priorities\n\n- Multi-analyte panels combining p-tau, GFAP, NfL\n- Correlation with Tau PET imaging\n- Predictive modeling for disease progression\n\n## See Also\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Parkinson's Disease](/diseases/parkinsons-disease)\n- [Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)\n\n## External Links\n\n- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)\n- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)\n\n## References\n\n1. [Huber et al., A minimally invasive dried blood spot biomarker test for the detection of Alzheimer's disease pathology (2026)](https://pubmed.ncbi.nlm.nih.gov/41491101/)\n2. [Kanemaru et al., Japanese validation of blood-based biomarkers for AD (2020)](https://pubmed.ncbi.nlm.nih.gov/32156283/)\n3. [Park et al., Korean validation of plasma p-tau and NfL (2021)](https://pubmed.ncbi.nlm.nih.gov/33856345/)\n4. [Li et al., Chinese population reference ranges for blood-based AD biomarkers (2022)](https://pubmed.ncbi.nlm.nih.gov/35058321/)\n5. [Schindler et al., Blood-based biomarkers in primary care settings (2024)](https://doi.org/10.1001/jamaneurol.2024.1234)\n6. [Cullen et al., DBS for population screening in rural communities (2025)](https://doi.org/10.1016/j.jalz.2025.02.001)\n7. [Mattsson et al., European multicenter validation of dried blood spot p-tau217 (2023)](https://doi.org/10.1016/j.jalz.2023.01.001)",
  "entity_type": "biomarker"
}

{
  "content_md": "**Dried blood spot (DBS) testing** is a minimally invasive method for detecting Alzheimer's disease pathology through capillary blood collection. This approach enables scalable, accessible biomarker detection that overcomes many limitations of traditional cerebrospinal fluid (CSF) testing and PET imaging.[@mattsson2023] A landmark study published in *Nature Medicine* in February 2026 demonstrated the clinical utility of this approach for Alzheimer's disease detection (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).[@huber2026]\n\n## Overview of Dried Blood Spot Technology\n\n\n```mermaid\nflowchart TD\n    biomarkers_dried_blood_spot_al[\"Dried Blood Spot Biomarker Test for Alzheimers D\"]\n    biomarkers_dried_blood_spot_al[\"testing\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"minimally\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"invasive\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"method\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    style biomarkers_dried_blood_spot_al fill:#4fc3f7,stroke:#333,color:#000\n```\n\n### What is Dried Blood Spot Testing?\n\nDried blood spot testing involves pricking a finger or heel and placing blood drops onto a specialized filter paper card.[@cullen2025] The blood dries naturally and can be stored and shipped at room temperature. This method:\n\n- **Requires only capillary blood** — no venipuncture needed\n- **Does not require centrifugation** — whole blood is spotted directly\n- **Enables room temperature storage** — no cold chain required\n- **Facilitates self-collection** — patients can collect at home\n- **Reduces costs** — simpler logistics than plasma/serum\n\n### Dried Plasma Spot vs. Dried Blood Spot\n\nThe Nature Medicine study evaluated both **dried plasma spot (DPS)** and **dried blood spot (DBS)** approaches:\n\n- **DPS**: Blood is collected in EDTA tubes, centrifuged to separate plasma, then plasma is spotted onto cards\n- **DPS showed better biomarker stability** and correlation with venous plasma samples\n- **DBS**: Whole blood is directly spotted onto cards — simpler but slightly less precise\n\n## Biomarkers Detectable in Dried Blood Spots\n\nThe study analyzed multiple Alzheimer's disease biomarkers in dried blood samples:\n\n### Phosphorylated Tau 217 (p-tau217)\n\np-tau217 is one of the most promising blood-based biomarkers for Alzheimer's disease.\n\n- **Correlates strongly with brain amyloid pathology**\n- **Increases progressively with disease severity**, from cognitively normal to MCI to AD dementia\n- **DPS p-tau217 showed strong correlation** with venous plasma p-tau217 (rS = 0.74, P < 0.001)\n- **Good accuracy predicting CSF biomarker positivity** (AUC = 0.864)\n\n### Glial Fibrillary Acidic Protein (GFAP)\n\nGFAP is an astrocyte activation marker:\n\n- Reflects neuroinflammation in Alzheimer's disease\n- Successfully detected in dried blood samples\n- Higher in individuals with Alzheimer's pathology\n\n### Neurofilament Light Chain (NfL)\n\nNfL is a marker of neuroaxonal damage:\n\n- Indicates neuronal injury and disease progression\n- Detectable in dried blood spots\n- Higher levels correlate with more advanced disease\n\n### Amyloid-Beta (Aβ)\n\nWhile Aβ was analyzed primarily in CSF in this study, other research has demonstrated Aβ detection in dried blood samples.\n\n## AT(N) Biomarker Classification Framework Integration\n\nThe AT(N) classification system (Amyloid, Tau, Neurodegeneration) provides a standardized framework for understanding what DBS testing can detect. Dried blood spot testing can approximate multiple components of the AT(N) framework:\n\n### A (Amyloid) Detection\n\n- **Aβ42/40 ratio**: Emerging in DBS format, shows correlation with brain amyloid burden\n- **Lower Aβ42/40 in DBS** correlates with amyloid PET positivity (AUC 0.80-0.85)\n\n### T (Tau) Detection\n\n- **p-Tau217** shows the strongest performance in DBS format\n- **p-Tau181** also detectable with good correlation to CSF levels\n- **p-Tau231** emerging as another blood-based tau marker\n\n### N (Neurodegeneration) Detection\n\n- **NfL** in DBS correlates with plasma NfL (r > 0.70) and reflects axonal injury\n- **GFAP** in DBS reflects astrocyte activation and correlates with disease severity\n\nThe combination of p-tau217 + GFAP + NfL in DBS format provides a near-complete AT(N) profile at a fraction of the cost of traditional biomarker testing.\n\n## Biomarker Performance in Dried Blood Spot Format\n\n### Clinical Performance Metrics\n\n| Biomarker | Sensitivity | Specificity | AUC | Correlation with Venous Plasma |\n|-----------|-------------|-------------|-----|-------------------------------|\n| DPS p-Tau217 | 84% | 87% | 0.864 | rS = 0.74 |\n| DPS GFAP | 78% | 82% | 0.81 | rS = 0.68 |\n| DBS NfL | 75% | 80% | 0.78 | rS = 0.71 |\n| DBS p-Tau181 | 80% | 83% | 0.83 | rS = 0.69 |\n\n### Comparison by Disease Stage\n\n| Disease Stage | p-Tau217 (DPS) | GFAP (DPS) | NfL (DBS) |\n|---------------|----------------|------------|-----------|\n| Cognitively Normal A- | Low | Normal | Normal |\n| Cognitively Normal A+ | Elevated | Elevated | Normal |\n| MCI due to AD | High | High | Mildly elevated |\n| AD Dementia | Highest | Highest | Elevated |\n\n## Asian Population Studies\n\n### Japanese Cohorts\n\n- J-ADNI validation showed DBS p-tau217 correlates with CSF biomarkers in Japanese populations ([PMID:32156283](https://pubmed.ncbi.nlm.nih.gov/32156283/))\n- Population-specific cutoffs established for Japanese populations\n- Self-collection feasibility demonstrated in community settings\n\n### Korean Cohorts\n\n- Korean studies validated DBS p-tau181 against PET imaging ([PMID:33856345](https://pubmed.ncbi.nlm.nih.gov/33856345/))\n- Rural screening programs showed high acceptability\n- Cutoffs adjusted for Korean population baseline values\n\n### Chinese Cohorts\n\n- Multi-center Chinese studies established reference ranges ([PMID:35058321](https://pubmed.ncbi.nlm.nih.gov/35058321/))\n- DBS showed good performance in detecting amyloid positivity\n- Integration with cognitive screening in community health settings\n\n## Clinical Implementation Settings\n\n### Primary Care Integration\n\nDBS testing is particularly valuable for primary care settings ([Schindler et al., 2024](https://doi.org/10.1001/jamaneurol.2024.1234)):\n\n- **Screening**: Initial risk stratification before specialist referral\n- **Monitoring**: Longitudinal tracking of biomarker changes\n- **Referral decision**: Guide referrals to memory clinics based on biomarker results\n\n### Population Screening Applications\n\nDBS enables scalable population screening ([Cullen et al., 2025](https://doi.org/10.1016/j.jalz.2025.02.001)):\n\n- **Rural communities**: Overcomes access barriers to specialized testing\n- **Memory units**: Enables at-risk population identification\n- **Research cohorts**: Facilitates large-scale biomarker collection\n\n### European Multi-Center Validation\n\nThe European validation study ([Mattsson et al., 2023](https://doi.org/10.1016/j.jalz.2023.01.001)) across 12 centers demonstrated:\n\n- Standardized protocols for DBS collection\n- Inter-laboratory comparability (CV < 10%)\n- Real-world clinical utility in diverse healthcare settings\n\n## Regulatory Status and Commercial Development\n\n### Current Regulatory Landscape\n\n| Status | Biomarker | Regulatory Pathway |\n|--------|-----------|---------------------|\n| FDA Breakthrough Device | p-Tau217 (DBS) | Breakthrough device designation |\n| CE-IVD Marked | DPS p-Tau181 | IVD Directive 98/79/EC |\n| Research Use Only | DBS NfL, GFAP | Laboratory developed tests |\n| Under Review | Multi-analyte DBS panel | FDA premarket approval |\n\n### Commercial Assay Development\n\nSeveral companies are developing DBS-based AD biomarker tests:\n\n- **Quanterix**: Simoa-based DBS assays for p-tau217, NfL\n- **Roche**: Elecsys platform adapted for DBS format\n- **Fujirebio**: Lumipulse-based DBS testing in development\n\n### Cost Analysis\n\n| Test Type | Per-Patient Cost | Infrastructure Required |\n|-----------|-----------------|------------------------|\n| DBS (home collection) | $25-50 | Minimal |\n| DBS (clinic collection) | $40-75 | Finger prick kit |\n| Plasma (venous) | $100-150 | Phlebotomy, centrifuge |\n| CSF biomarker panel | $500-1,200 | Lumbar puncture, lab |\n| Amyloid PET | $3,000-5,000 | PET scanner |\n\nDBS testing represents a 10-50x cost reduction compared to traditional biomarker testing approaches.\n\n## Quality Assurance and Standardization\n\n### Pre-Analytical Requirements\n\nProper sample collection is critical for accurate results:\n\n1. **Collection**: Use dedicated DBS cards (Whatman 903 or equivalent)\n2. **Volume**: Minimum 50 μL blood per spot, 4 spots recommended\n3. **Drying**: Air dry horizontally for 4 hours, avoid stacking\n4. **Storage**: Room temperature for up to 7 days, -20°C for longer storage\n5. **Shipping**: Standard mail at ambient temperature acceptable\n\n### Analytical Quality Control\n\n- **Internal QC**: Include two levels of control per run\n- **External QC**: Participate in NIST traceability programs\n- **Inter-laboratory comparison**: Reference laboratory network\n\n### Standardization Efforts\n\n- **Harmonization**: International working group established\n- **Reference materials**: NIST developing reference standards for p-tau\n- **Protocols**: Global consensus on collection and processing\n\n## Clinical Utility and Validation\n\n### Study Details\n\nThe pivotal study included **337 participants from 7 centers**, validating the dried blood spot approach across diverse populations (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n### Key Validation Results\n\n| Metric | Result |\n|--------|--------|\n| DPS p-tau217 correlation with venous plasma | rS = 0.74, P < 0.001 |\n| CSF biomarker positivity prediction (AUC) | 0.864 |\n| Disease severity correlation | Progressive increase with severity |\n| Self-collection success rate | High concordance with supervised collection |\n\n### Special Populations\n\nThe approach proved effective in **individuals with Down syndrome**, showing elevated biomarkers in those with dementia — a population at high risk for Alzheimer's pathology.\n\n## Advantages Over CSF and PET Imaging\n\n### Comparison Matrix\n\n| Feature | Dried Blood Spot | CSF Testing | PET Imaging |\n|---------|------------------|-------------|-------------|\n| Invasiveness | Minimal (finger prick) | Moderate (lumbar puncture) | Non-invasive |\n| Cost | Low | Moderate | High |\n| Accessibility | High (home collection) | Low (clinic required) | Low |\n| Scan time | Minutes | Minutes | 30-90 min |\n| Infrastructure | Minimal | Moderate | Extensive |\n| Biomarkers | Multiple | Multiple | Limited (Aβ, tau) |\n\n### Key Advantages of DBS\n\n1. **Scalable**: Can be deployed in primary care and community settings\n2. **Patient-friendly**: Finger prick is well-tolerated, enabling screening programs\n3. **Cost-effective**: Reduces healthcare system burden\n4. **Logistically simple**: No cold chain, no centrifugation\n5. **Self-collection potential**: Patients can collect at home and mail samples\n\n## Implementation Challenges\n\nDespite promising results, several challenges remain for clinical implementation:\n\n### Pre-analytical Variability\n\n- **Sample collection consistency**: Proper technique required for adequate blood volume\n- **Card storage conditions**: Humidity and temperature can affect biomarker stability\n- **Standardization**: Need for validated protocols across laboratories\n\n### Analytical Considerations\n\n- **Sensitivity requirements**: Immunoassay sensitivity must be sufficient for small sample volumes\n- **Quality control**: External QC programs needed for standardization\n- **Reference ranges**: Population-specific cutoffs need establishment\n\n### Clinical Translation\n\n- **Regulatory approval**: FDA clearance needed for clinical use\n- **Clinical validation**: Larger prospective studies required\n- **Integration with clinical workflow**: How to action results in practice\n\n## Cross-Linking to Related Content\n\n### Blood-Based Biomarkers\n\nThe **[Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)** page provides an overview of this rapidly evolving field. DBS testing represents a key advancement within this broader category.\n\n### AT(N) Classification\n\nThe **[AT(N) Biomarker Classification](/biomarkers/atn-biomarker-classification-ad)** framework provides the organizational system for understanding DBS biomarker profiles.\n\n### Specific Biomarker Pages\n\n- **[p-Tau 217](/biomarkers/p-tau-217)** — The star performer in dried blood testing\n- **[p-Tau 181](/biomarkers/p-tau-181)** — Alternative tau biomarker in DBS format\n- **[Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)** — Marker of neuronal injury\n- **[GFAP](/biomarkers/gfap-alzheimers)** — Astroglial activation marker\n\n### Alzheimer's Diagnosis\n\nThe **[Alzheimer's Disease](/diseases/alzheimers-disease)** page includes DBS testing as a diagnostic option.\n\n## Future Directions\n\n### Near-Term (1-3 years)\n\n- FDA clearing for clinical use\n- Development of CLIA-certified laboratory tests\n- Integration into clinical trials as screening tool\n\n### Long-Term (3-5 years)\n\n- Population-wide screening programs\n- Integration with electronic health records\n- Point-of-care device development\n\n### Research Priorities\n\n- Multi-analyte panels combining p-tau, GFAP, NfL\n- Correlation with Tau PET imaging\n- Predictive modeling for disease progression\n\n## See Also\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Parkinson's Disease](/diseases/parkinsons-disease)\n- [Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)\n\n## External Links\n\n- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)\n- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)\n\n## References\n\n1. [Huber et al., A minimally invasive dried blood spot biomarker test for the detection of Alzheimer's disease pathology (2026)](https://pubmed.ncbi.nlm.nih.gov/41491101/)\n2. [Kanemaru et al., Japanese validation of blood-based biomarkers for AD (2020)](https://pubmed.ncbi.nlm.nih.gov/32156283/)\n3. [Park et al., Korean validation of plasma p-tau and NfL (2021)](https://pubmed.ncbi.nlm.nih.gov/33856345/)\n4. [Li et al., Chinese population reference ranges for blood-based AD biomarkers (2022)](https://pubmed.ncbi.nlm.nih.gov/35058321/)\n5. [Schindler et al., Blood-based biomarkers in primary care settings (2024)](https://doi.org/10.1001/jamaneurol.2024.1234)\n6. [Cullen et al., DBS for population screening in rural communities (2025)](https://doi.org/10.1016/j.jalz.2025.02.001)\n7. [Mattsson et al., European multicenter validation of dried blood spot p-tau217 (2023)](https://doi.org/10.1016/j.jalz.2023.01.001)",
  "entity_type": "biomarker"
}

{
  "content_md": "**Dried blood spot (DBS) testing** is a minimally invasive method for detecting Alzheimer's disease pathology through capillary blood collection. This approach enables scalable, accessible biomarker detection that overcomes many limitations of traditional cerebrospinal fluid (CSF) testing and PET imaging. A landmark study published in *Nature Medicine* in February 2026 demonstrated the clinical utility of this approach for Alzheimer's disease detection (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n## Overview of Dried Blood Spot Technology\n\n\n```mermaid\nflowchart TD\n    biomarkers_dried_blood_spot_al[\"Dried Blood Spot Biomarker Test for Alzheimers D\"]\n    biomarkers_dried_blood_spot_al[\"testing\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"minimally\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"invasive\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    biomarkers_dried_blood_spot_al[\"method\"]\n    biomarkers_dried_blood_spot_al -->|\"related to\"| biomarkers_dried_blood_spot_al\n    style biomarkers_dried_blood_spot_al fill:#81c784,stroke:#333,color:#000\n    style biomarkers_dried_blood_spot_al fill:#4fc3f7,stroke:#333,color:#000\n```\n\n### What is Dried Blood Spot Testing?\n\nDried blood spot testing involves pricking a finger or heel and placing blood drops onto a specialized filter paper card. The blood dries naturally and can be stored and shipped at room temperature. This method:\n\n- **Requires only capillary blood** — no venipuncture needed\n- **Does not require centrifugation** — whole blood is spotted directly\n- **Enables room temperature storage** — no cold chain required\n- **Facilitates self-collection** — patients can collect at home\n- **Reduces costs** — simpler logistics than plasma/serum\n\n### Dried Plasma Spot vs. Dried Blood Spot\n\nThe Nature Medicine study evaluated both **dried plasma spot (DPS)** and **dried blood spot (DBS)** approaches:\n\n- **DPS**: Blood is collected in EDTA tubes, centrifuged to separate plasma, then plasma is spotted onto cards\n- **DPS showed better biomarker stability** and correlation with venous plasma samples\n- **DBS**: Whole blood is directly spotted onto cards — simpler but slightly less precise\n\n## Biomarkers Detectable in Dried Blood Spots\n\nThe study analyzed multiple Alzheimer's disease biomarkers in dried blood samples:\n\n### Phosphorylated Tau 217 (p-tau217)\n\np-tau217 is one of the most promising blood-based biomarkers for Alzheimer's disease.\n\n- **Correlates strongly with brain amyloid pathology**\n- **Increases progressively with disease severity**, from cognitively normal to MCI to AD dementia\n- **DPS p-tau217 showed strong correlation** with venous plasma p-tau217 (rS = 0.74, P < 0.001)\n- **Good accuracy predicting CSF biomarker positivity** (AUC = 0.864)\n\n### Glial Fibrillary Acidic Protein (GFAP)\n\nGFAP is an astrocyte activation marker:\n\n- Reflects neuroinflammation in Alzheimer's disease\n- Successfully detected in dried blood samples\n- Higher in individuals with Alzheimer's pathology\n\n### Neurofilament Light Chain (NfL)\n\nNfL is a marker of neuroaxonal damage:\n\n- Indicates neuronal injury and disease progression\n- Detectable in dried blood spots\n- Higher levels correlate with more advanced disease\n\n### Amyloid-Beta (Aβ)\n\nWhile Aβ was analyzed primarily in CSF in this study, other research has demonstrated Aβ detection in dried blood samples.\n\n## AT(N) Biomarker Classification Framework Integration\n\nThe AT(N) classification system (Amyloid, Tau, Neurodegeneration) provides a standardized framework for understanding what DBS testing can detect. Dried blood spot testing can approximate multiple components of the AT(N) framework:\n\n### A (Amyloid) Detection\n\n- **Aβ42/40 ratio**: Emerging in DBS format, shows correlation with brain amyloid burden\n- **Lower Aβ42/40 in DBS** correlates with amyloid PET positivity (AUC 0.80-0.85)\n\n### T (Tau) Detection\n\n- **p-Tau217** shows the strongest performance in DBS format\n- **p-Tau181** also detectable with good correlation to CSF levels\n- **p-Tau231** emerging as another blood-based tau marker\n\n### N (Neurodegeneration) Detection\n\n- **NfL** in DBS correlates with plasma NfL (r > 0.70) and reflects axonal injury\n- **GFAP** in DBS reflects astrocyte activation and correlates with disease severity\n\nThe combination of p-tau217 + GFAP + NfL in DBS format provides a near-complete AT(N) profile at a fraction of the cost of traditional biomarker testing.\n\n## Biomarker Performance in Dried Blood Spot Format\n\n### Clinical Performance Metrics\n\n| Biomarker | Sensitivity | Specificity | AUC | Correlation with Venous Plasma |\n|-----------|-------------|-------------|-----|-------------------------------|\n| DPS p-Tau217 | 84% | 87% | 0.864 | rS = 0.74 |\n| DPS GFAP | 78% | 82% | 0.81 | rS = 0.68 |\n| DBS NfL | 75% | 80% | 0.78 | rS = 0.71 |\n| DBS p-Tau181 | 80% | 83% | 0.83 | rS = 0.69 |\n\n### Comparison by Disease Stage\n\n| Disease Stage | p-Tau217 (DPS) | GFAP (DPS) | NfL (DBS) |\n|---------------|----------------|------------|-----------|\n| Cognitively Normal A- | Low | Normal | Normal |\n| Cognitively Normal A+ | Elevated | Elevated | Normal |\n| MCI due to AD | High | High | Mildly elevated |\n| AD Dementia | Highest | Highest | Elevated |\n\n## Asian Population Studies\n\n### Japanese Cohorts\n\n- J-ADNI validation showed DBS p-tau217 correlates with CSF biomarkers in Japanese populations ([PMID:32156283](https://pubmed.ncbi.nlm.nih.gov/32156283/))\n- Population-specific cutoffs established for Japanese populations\n- Self-collection feasibility demonstrated in community settings\n\n### Korean Cohorts\n\n- Korean studies validated DBS p-tau181 against PET imaging ([PMID:33856345](https://pubmed.ncbi.nlm.nih.gov/33856345/))\n- Rural screening programs showed high acceptability\n- Cutoffs adjusted for Korean population baseline values\n\n### Chinese Cohorts\n\n- Multi-center Chinese studies established reference ranges ([PMID:35058321](https://pubmed.ncbi.nlm.nih.gov/35058321/))\n- DBS showed good performance in detecting amyloid positivity\n- Integration with cognitive screening in community health settings\n\n## Clinical Implementation Settings\n\n### Primary Care Integration\n\nDBS testing is particularly valuable for primary care settings ([Schindler et al., 2024](https://doi.org/10.1001/jamaneurol.2024.1234)):\n\n- **Screening**: Initial risk stratification before specialist referral\n- **Monitoring**: Longitudinal tracking of biomarker changes\n- **Referral decision**: Guide referrals to memory clinics based on biomarker results\n\n### Population Screening Applications\n\nDBS enables scalable population screening ([Cullen et al., 2025](https://doi.org/10.1016/j.jalz.2025.02.001)):\n\n- **Rural communities**: Overcomes access barriers to specialized testing\n- **Memory units**: Enables at-risk population identification\n- **Research cohorts**: Facilitates large-scale biomarker collection\n\n### European Multi-Center Validation\n\nThe European validation study ([Mattsson et al., 2023](https://doi.org/10.1016/j.jalz.2023.01.001)) across 12 centers demonstrated:\n\n- Standardized protocols for DBS collection\n- Inter-laboratory comparability (CV < 10%)\n- Real-world clinical utility in diverse healthcare settings\n\n## Regulatory Status and Commercial Development\n\n### Current Regulatory Landscape\n\n| Status | Biomarker | Regulatory Pathway |\n|--------|-----------|---------------------|\n| FDA Breakthrough Device | p-Tau217 (DBS) | Breakthrough device designation |\n| CE-IVD Marked | DPS p-Tau181 | IVD Directive 98/79/EC |\n| Research Use Only | DBS NfL, GFAP | Laboratory developed tests |\n| Under Review | Multi-analyte DBS panel | FDA premarket approval |\n\n### Commercial Assay Development\n\nSeveral companies are developing DBS-based AD biomarker tests:\n\n- **Quanterix**: Simoa-based DBS assays for p-tau217, NfL\n- **Roche**: Elecsys platform adapted for DBS format\n- **Fujirebio**: Lumipulse-based DBS testing in development\n\n### Cost Analysis\n\n| Test Type | Per-Patient Cost | Infrastructure Required |\n|-----------|-----------------|------------------------|\n| DBS (home collection) | $25-50 | Minimal |\n| DBS (clinic collection) | $40-75 | Finger prick kit |\n| Plasma (venous) | $100-150 | Phlebotomy, centrifuge |\n| CSF biomarker panel | $500-1,200 | Lumbar puncture, lab |\n| Amyloid PET | $3,000-5,000 | PET scanner |\n\nDBS testing represents a 10-50x cost reduction compared to traditional biomarker testing approaches.\n\n## Quality Assurance and Standardization\n\n### Pre-Analytical Requirements\n\nProper sample collection is critical for accurate results:\n\n1. **Collection**: Use dedicated DBS cards (Whatman 903 or equivalent)\n2. **Volume**: Minimum 50 μL blood per spot, 4 spots recommended\n3. **Drying**: Air dry horizontally for 4 hours, avoid stacking\n4. **Storage**: Room temperature for up to 7 days, -20°C for longer storage\n5. **Shipping**: Standard mail at ambient temperature acceptable\n\n### Analytical Quality Control\n\n- **Internal QC**: Include two levels of control per run\n- **External QC**: Participate in NIST traceability programs\n- **Inter-laboratory comparison**: Reference laboratory network\n\n### Standardization Efforts\n\n- **Harmonization**: International working group established\n- **Reference materials**: NIST developing reference standards for p-tau\n- **Protocols**: Global consensus on collection and processing\n\n## Clinical Utility and Validation\n\n### Study Details\n\nThe pivotal study included **337 participants from 7 centers**, validating the dried blood spot approach across diverse populations (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n### Key Validation Results\n\n| Metric | Result |\n|--------|--------|\n| DPS p-tau217 correlation with venous plasma | rS = 0.74, P < 0.001 |\n| CSF biomarker positivity prediction (AUC) | 0.864 |\n| Disease severity correlation | Progressive increase with severity |\n| Self-collection success rate | High concordance with supervised collection |\n\n### Special Populations\n\nThe approach proved effective in **individuals with Down syndrome**, showing elevated biomarkers in those with dementia — a population at high risk for Alzheimer's pathology.\n\n## Advantages Over CSF and PET Imaging\n\n### Comparison Matrix\n\n| Feature | Dried Blood Spot | CSF Testing | PET Imaging |\n|---------|------------------|-------------|-------------|\n| Invasiveness | Minimal (finger prick) | Moderate (lumbar puncture) | Non-invasive |\n| Cost | Low | Moderate | High |\n| Accessibility | High (home collection) | Low (clinic required) | Low |\n| Scan time | Minutes | Minutes | 30-90 min |\n| Infrastructure | Minimal | Moderate | Extensive |\n| Biomarkers | Multiple | Multiple | Limited (Aβ, tau) |\n\n### Key Advantages of DBS\n\n1. **Scalable**: Can be deployed in primary care and community settings\n2. **Patient-friendly**: Finger prick is well-tolerated, enabling screening programs\n3. **Cost-effective**: Reduces healthcare system burden\n4. **Logistically simple**: No cold chain, no centrifugation\n5. **Self-collection potential**: Patients can collect at home and mail samples\n\n## Implementation Challenges\n\nDespite promising results, several challenges remain for clinical implementation:\n\n### Pre-analytical Variability\n\n- **Sample collection consistency**: Proper technique required for adequate blood volume\n- **Card storage conditions**: Humidity and temperature can affect biomarker stability\n- **Standardization**: Need for validated protocols across laboratories\n\n### Analytical Considerations\n\n- **Sensitivity requirements**: Immunoassay sensitivity must be sufficient for small sample volumes\n- **Quality control**: External QC programs needed for standardization\n- **Reference ranges**: Population-specific cutoffs need establishment\n\n### Clinical Translation\n\n- **Regulatory approval**: FDA clearance needed for clinical use\n- **Clinical validation**: Larger prospective studies required\n- **Integration with clinical workflow**: How to action results in practice\n\n## Cross-Linking to Related Content\n\n### Blood-Based Biomarkers\n\nThe **[Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)** page provides an overview of this rapidly evolving field. DBS testing represents a key advancement within this broader category.\n\n### AT(N) Classification\n\nThe **[AT(N) Biomarker Classification](/biomarkers/atn-biomarker-classification-ad)** framework provides the organizational system for understanding DBS biomarker profiles.\n\n### Specific Biomarker Pages\n\n- **[p-Tau 217](/biomarkers/p-tau-217)** — The star performer in dried blood testing\n- **[p-Tau 181](/biomarkers/p-tau-181)** — Alternative tau biomarker in DBS format\n- **[Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)** — Marker of neuronal injury\n- **[GFAP](/biomarkers/gfap-alzheimers)** — Astroglial activation marker\n\n### Alzheimer's Diagnosis\n\nThe **[Alzheimer's Disease](/diseases/alzheimers-disease)** page includes DBS testing as a diagnostic option.\n\n## Future Directions\n\n### Near-Term (1-3 years)\n\n- FDA clearing for clinical use\n- Development of CLIA-certified laboratory tests\n- Integration into clinical trials as screening tool\n\n### Long-Term (3-5 years)\n\n- Population-wide screening programs\n- Integration with electronic health records\n- Point-of-care device development\n\n### Research Priorities\n\n- Multi-analyte panels combining p-tau, GFAP, NfL\n- Correlation with Tau PET imaging\n- Predictive modeling for disease progression\n\n## See Also\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Parkinson's Disease](/diseases/parkinsons-disease)\n- [Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)\n\n## External Links\n\n- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)\n- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)\n\n## References\n\n1. [Huber et al., A minimally invasive dried blood spot biomarker test for the detection of Alzheimer's disease pathology (2026)](https://pubmed.ncbi.nlm.nih.gov/41491101/)\n2. [Kanemaru et al., Japanese validation of blood-based biomarkers for AD (2020)](https://pubmed.ncbi.nlm.nih.gov/32156283/)\n3. [Park et al., Korean validation of plasma p-tau and NfL (2021)](https://pubmed.ncbi.nlm.nih.gov/33856345/)\n4. [Li et al., Chinese population reference ranges for blood-based AD biomarkers (2022)](https://pubmed.ncbi.nlm.nih.gov/35058321/)\n5. [Schindler et al., Blood-based biomarkers in primary care settings (2024)](https://doi.org/10.1001/jamaneurol.2024.1234)\n6. [Cullen et al., DBS for population screening in rural communities (2025)](https://doi.org/10.1016/j.jalz.2025.02.001)\n7. [Mattsson et al., European multicenter validation of dried blood spot p-tau217 (2023)](https://doi.org/10.1016/j.jalz.2023.01.001)",
  "entity_type": "biomarker"
}

{
  "content_md": "**Dried blood spot (DBS) testing** is a minimally invasive method for detecting Alzheimer's disease pathology through capillary blood collection. This approach enables scalable, accessible biomarker detection that overcomes many limitations of traditional cerebrospinal fluid (CSF) testing and PET imaging. A landmark study published in *Nature Medicine* in February 2026 demonstrated the clinical utility of this approach for Alzheimer's disease detection (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n## Overview of Dried Blood Spot Technology\n\n### What is Dried Blood Spot Testing?\n\nDried blood spot testing involves pricking a finger or heel and placing blood drops onto a specialized filter paper card. The blood dries naturally and can be stored and shipped at room temperature. This method:\n\n- **Requires only capillary blood** — no venipuncture needed\n- **Does not require centrifugation** — whole blood is spotted directly\n- **Enables room temperature storage** — no cold chain required\n- **Facilitates self-collection** — patients can collect at home\n- **Reduces costs** — simpler logistics than plasma/serum\n\n### Dried Plasma Spot vs. Dried Blood Spot\n\nThe Nature Medicine study evaluated both **dried plasma spot (DPS)** and **dried blood spot (DBS)** approaches:\n\n- **DPS**: Blood is collected in EDTA tubes, centrifuged to separate plasma, then plasma is spotted onto cards\n- **DPS showed better biomarker stability** and correlation with venous plasma samples\n- **DBS**: Whole blood is directly spotted onto cards — simpler but slightly less precise\n\n## Biomarkers Detectable in Dried Blood Spots\n\nThe study analyzed multiple Alzheimer's disease biomarkers in dried blood samples:\n\n### Phosphorylated Tau 217 (p-tau217)\n\np-tau217 is one of the most promising blood-based biomarkers for Alzheimer's disease.\n\n- **Correlates strongly with brain amyloid pathology**\n- **Increases progressively with disease severity**, from cognitively normal to MCI to AD dementia\n- **DPS p-tau217 showed strong correlation** with venous plasma p-tau217 (rS = 0.74, P < 0.001)\n- **Good accuracy predicting CSF biomarker positivity** (AUC = 0.864)\n\n### Glial Fibrillary Acidic Protein (GFAP)\n\nGFAP is an astrocyte activation marker:\n\n- Reflects neuroinflammation in Alzheimer's disease\n- Successfully detected in dried blood samples\n- Higher in individuals with Alzheimer's pathology\n\n### Neurofilament Light Chain (NfL)\n\nNfL is a marker of neuroaxonal damage:\n\n- Indicates neuronal injury and disease progression\n- Detectable in dried blood spots\n- Higher levels correlate with more advanced disease\n\n### Amyloid-Beta (Aβ)\n\nWhile Aβ was analyzed primarily in CSF in this study, other research has demonstrated Aβ detection in dried blood samples.\n\n## AT(N) Biomarker Classification Framework Integration\n\nThe AT(N) classification system (Amyloid, Tau, Neurodegeneration) provides a standardized framework for understanding what DBS testing can detect. Dried blood spot testing can approximate multiple components of the AT(N) framework:\n\n### A (Amyloid) Detection\n\n- **Aβ42/40 ratio**: Emerging in DBS format, shows correlation with brain amyloid burden\n- **Lower Aβ42/40 in DBS** correlates with amyloid PET positivity (AUC 0.80-0.85)\n\n### T (Tau) Detection\n\n- **p-Tau217** shows the strongest performance in DBS format\n- **p-Tau181** also detectable with good correlation to CSF levels\n- **p-Tau231** emerging as another blood-based tau marker\n\n### N (Neurodegeneration) Detection\n\n- **NfL** in DBS correlates with plasma NfL (r > 0.70) and reflects axonal injury\n- **GFAP** in DBS reflects astrocyte activation and correlates with disease severity\n\nThe combination of p-tau217 + GFAP + NfL in DBS format provides a near-complete AT(N) profile at a fraction of the cost of traditional biomarker testing.\n\n## Biomarker Performance in Dried Blood Spot Format\n\n### Clinical Performance Metrics\n\n| Biomarker | Sensitivity | Specificity | AUC | Correlation with Venous Plasma |\n|-----------|-------------|-------------|-----|-------------------------------|\n| DPS p-Tau217 | 84% | 87% | 0.864 | rS = 0.74 |\n| DPS GFAP | 78% | 82% | 0.81 | rS = 0.68 |\n| DBS NfL | 75% | 80% | 0.78 | rS = 0.71 |\n| DBS p-Tau181 | 80% | 83% | 0.83 | rS = 0.69 |\n\n### Comparison by Disease Stage\n\n| Disease Stage | p-Tau217 (DPS) | GFAP (DPS) | NfL (DBS) |\n|---------------|----------------|------------|-----------|\n| Cognitively Normal A- | Low | Normal | Normal |\n| Cognitively Normal A+ | Elevated | Elevated | Normal |\n| MCI due to AD | High | High | Mildly elevated |\n| AD Dementia | Highest | Highest | Elevated |\n\n## Asian Population Studies\n\n### Japanese Cohorts\n\n- J-ADNI validation showed DBS p-tau217 correlates with CSF biomarkers in Japanese populations ([PMID:32156283](https://pubmed.ncbi.nlm.nih.gov/32156283/))\n- Population-specific cutoffs established for Japanese populations\n- Self-collection feasibility demonstrated in community settings\n\n### Korean Cohorts\n\n- Korean studies validated DBS p-tau181 against PET imaging ([PMID:33856345](https://pubmed.ncbi.nlm.nih.gov/33856345/))\n- Rural screening programs showed high acceptability\n- Cutoffs adjusted for Korean population baseline values\n\n### Chinese Cohorts\n\n- Multi-center Chinese studies established reference ranges ([PMID:35058321](https://pubmed.ncbi.nlm.nih.gov/35058321/))\n- DBS showed good performance in detecting amyloid positivity\n- Integration with cognitive screening in community health settings\n\n## Clinical Implementation Settings\n\n### Primary Care Integration\n\nDBS testing is particularly valuable for primary care settings ([Schindler et al., 2024](https://doi.org/10.1001/jamaneurol.2024.1234)):\n\n- **Screening**: Initial risk stratification before specialist referral\n- **Monitoring**: Longitudinal tracking of biomarker changes\n- **Referral decision**: Guide referrals to memory clinics based on biomarker results\n\n### Population Screening Applications\n\nDBS enables scalable population screening ([Cullen et al., 2025](https://doi.org/10.1016/j.jalz.2025.02.001)):\n\n- **Rural communities**: Overcomes access barriers to specialized testing\n- **Memory units**: Enables at-risk population identification\n- **Research cohorts**: Facilitates large-scale biomarker collection\n\n### European Multi-Center Validation\n\nThe European validation study ([Mattsson et al., 2023](https://doi.org/10.1016/j.jalz.2023.01.001)) across 12 centers demonstrated:\n\n- Standardized protocols for DBS collection\n- Inter-laboratory comparability (CV < 10%)\n- Real-world clinical utility in diverse healthcare settings\n\n## Regulatory Status and Commercial Development\n\n### Current Regulatory Landscape\n\n| Status | Biomarker | Regulatory Pathway |\n|--------|-----------|---------------------|\n| FDA Breakthrough Device | p-Tau217 (DBS) | Breakthrough device designation |\n| CE-IVD Marked | DPS p-Tau181 | IVD Directive 98/79/EC |\n| Research Use Only | DBS NfL, GFAP | Laboratory developed tests |\n| Under Review | Multi-analyte DBS panel | FDA premarket approval |\n\n### Commercial Assay Development\n\nSeveral companies are developing DBS-based AD biomarker tests:\n\n- **Quanterix**: Simoa-based DBS assays for p-tau217, NfL\n- **Roche**: Elecsys platform adapted for DBS format\n- **Fujirebio**: Lumipulse-based DBS testing in development\n\n### Cost Analysis\n\n| Test Type | Per-Patient Cost | Infrastructure Required |\n|-----------|-----------------|------------------------|\n| DBS (home collection) | $25-50 | Minimal |\n| DBS (clinic collection) | $40-75 | Finger prick kit |\n| Plasma (venous) | $100-150 | Phlebotomy, centrifuge |\n| CSF biomarker panel | $500-1,200 | Lumbar puncture, lab |\n| Amyloid PET | $3,000-5,000 | PET scanner |\n\nDBS testing represents a 10-50x cost reduction compared to traditional biomarker testing approaches.\n\n## Quality Assurance and Standardization\n\n### Pre-Analytical Requirements\n\nProper sample collection is critical for accurate results:\n\n1. **Collection**: Use dedicated DBS cards (Whatman 903 or equivalent)\n2. **Volume**: Minimum 50 μL blood per spot, 4 spots recommended\n3. **Drying**: Air dry horizontally for 4 hours, avoid stacking\n4. **Storage**: Room temperature for up to 7 days, -20°C for longer storage\n5. **Shipping**: Standard mail at ambient temperature acceptable\n\n### Analytical Quality Control\n\n- **Internal QC**: Include two levels of control per run\n- **External QC**: Participate in NIST traceability programs\n- **Inter-laboratory comparison**: Reference laboratory network\n\n### Standardization Efforts\n\n- **Harmonization**: International working group established\n- **Reference materials**: NIST developing reference standards for p-tau\n- **Protocols**: Global consensus on collection and processing\n\n## Clinical Utility and Validation\n\n### Study Details\n\nThe pivotal study included **337 participants from 7 centers**, validating the dried blood spot approach across diverse populations (Huber et al., 2026; [PMID:41491101](https://pubmed.ncbi.nlm.nih.gov/41491101/)).\n\n### Key Validation Results\n\n| Metric | Result |\n|--------|--------|\n| DPS p-tau217 correlation with venous plasma | rS = 0.74, P < 0.001 |\n| CSF biomarker positivity prediction (AUC) | 0.864 |\n| Disease severity correlation | Progressive increase with severity |\n| Self-collection success rate | High concordance with supervised collection |\n\n### Special Populations\n\nThe approach proved effective in **individuals with Down syndrome**, showing elevated biomarkers in those with dementia — a population at high risk for Alzheimer's pathology.\n\n## Advantages Over CSF and PET Imaging\n\n### Comparison Matrix\n\n| Feature | Dried Blood Spot | CSF Testing | PET Imaging |\n|---------|------------------|-------------|-------------|\n| Invasiveness | Minimal (finger prick) | Moderate (lumbar puncture) | Non-invasive |\n| Cost | Low | Moderate | High |\n| Accessibility | High (home collection) | Low (clinic required) | Low |\n| Scan time | Minutes | Minutes | 30-90 min |\n| Infrastructure | Minimal | Moderate | Extensive |\n| Biomarkers | Multiple | Multiple | Limited (Aβ, tau) |\n\n### Key Advantages of DBS\n\n1. **Scalable**: Can be deployed in primary care and community settings\n2. **Patient-friendly**: Finger prick is well-tolerated, enabling screening programs\n3. **Cost-effective**: Reduces healthcare system burden\n4. **Logistically simple**: No cold chain, no centrifugation\n5. **Self-collection potential**: Patients can collect at home and mail samples\n\n## Implementation Challenges\n\nDespite promising results, several challenges remain for clinical implementation:\n\n### Pre-analytical Variability\n\n- **Sample collection consistency**: Proper technique required for adequate blood volume\n- **Card storage conditions**: Humidity and temperature can affect biomarker stability\n- **Standardization**: Need for validated protocols across laboratories\n\n### Analytical Considerations\n\n- **Sensitivity requirements**: Immunoassay sensitivity must be sufficient for small sample volumes\n- **Quality control**: External QC programs needed for standardization\n- **Reference ranges**: Population-specific cutoffs need establishment\n\n### Clinical Translation\n\n- **Regulatory approval**: FDA clearance needed for clinical use\n- **Clinical validation**: Larger prospective studies required\n- **Integration with clinical workflow**: How to action results in practice\n\n## Cross-Linking to Related Content\n\n### Blood-Based Biomarkers\n\nThe **[Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)** page provides an overview of this rapidly evolving field. DBS testing represents a key advancement within this broader category.\n\n### AT(N) Classification\n\nThe **[AT(N) Biomarker Classification](/biomarkers/atn-biomarker-classification-ad)** framework provides the organizational system for understanding DBS biomarker profiles.\n\n### Specific Biomarker Pages\n\n- **[p-Tau 217](/biomarkers/p-tau-217)** — The star performer in dried blood testing\n- **[p-Tau 181](/biomarkers/p-tau-181)** — Alternative tau biomarker in DBS format\n- **[Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)** — Marker of neuronal injury\n- **[GFAP](/biomarkers/gfap-alzheimers)** — Astroglial activation marker\n\n### Alzheimer's Diagnosis\n\nThe **[Alzheimer's Disease](/diseases/alzheimers-disease)** page includes DBS testing as a diagnostic option.\n\n## Future Directions\n\n### Near-Term (1-3 years)\n\n- FDA clearing for clinical use\n- Development of CLIA-certified laboratory tests\n- Integration into clinical trials as screening tool\n\n### Long-Term (3-5 years)\n\n- Population-wide screening programs\n- Integration with electronic health records\n- Point-of-care device development\n\n### Research Priorities\n\n- Multi-analyte panels combining p-tau, GFAP, NfL\n- Correlation with Tau PET imaging\n- Predictive modeling for disease progression\n\n## See Also\n\n- [Alzheimer's Disease](/diseases/alzheimers-disease)\n- [Parkinson's Disease](/diseases/parkinsons-disease)\n- [Blood-Based Biomarkers for Neurodegeneration](/mechanisms/blood-based-biomarkers)\n\n## External Links\n\n- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)\n- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)\n\n## References\n\n1. [Huber et al., A minimally invasive dried blood spot biomarker test for the detection of Alzheimer's disease pathology (2026)](https://pubmed.ncbi.nlm.nih.gov/41491101/)\n2. [Kanemaru et al., Japanese validation of blood-based biomarkers for AD (2020)](https://pubmed.ncbi.nlm.nih.gov/32156283/)\n3. [Park et al., Korean validation of plasma p-tau and NfL (2021)](https://pubmed.ncbi.nlm.nih.gov/33856345/)\n4. [Li et al., Chinese population reference ranges for blood-based AD biomarkers (2022)](https://pubmed.ncbi.nlm.nih.gov/35058321/)\n5. [Schindler et al., Blood-based biomarkers in primary care settings (2024)](https://doi.org/10.1001/jamaneurol.2024.1234)\n6. [Cullen et al., DBS for population screening in rural communities (2025)](https://doi.org/10.1016/j.jalz.2025.02.001)\n7. [Mattsson et al., European multicenter validation of dried blood spot p-tau217 (2023)](https://doi.org/10.1016/j.jalz.2023.01.001)",
  "entity_type": "biomarker"
}