Alzheimer's disease (AD) is the most common form of dementia, affecting an estimated 6.7 million people in the United States (1). The defining neuropathologies of AD are extracellular Aβ-plaques and intracellular neurofibrillary tangles (NFTs). Newly proposed guidance from the Alzheimer's Association recommends blood-based biomarker tests as a more affordable and accessible AD diagnostic aid (2). ALZ Blood Test is designed to make advanced biomarker testing accessible and useful when cognitive concerns warrant action.
White Paper
Alzheimer's Disease Biomarkers
A concise overview of key blood and CSF biomarkers used in Alzheimer's disease assessment.
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Evidence-led clinician leave-behind
Blood and CSF biomarkers help characterize amyloid pathology, tau pathology, neurodegeneration, and astrocyte activation within a broader clinical evaluation.
pTau-217
Plasma pTau-217 levels correlate with tau-PET imaging and are more sensitive and specific than pTau-181 in distinguishing AD from other neurodegenerative disorders. Clinical performance was determined using plasma samples from amyloid PET(+) and (-) subjects.
| Metric | Value |
|---|---|
| AMR (ng/L) | 0.007 - 10 |
| AUC | 0.95 |
| Cut-off (ng/L) | 0.63 |
| Specificity | 95.3% |
| Sensitivity | 95.8% |
| Stability | ≤ 48 hours 37°C; ≤ 1 week 21°C; ≤ 1 week 4°C; ≤ 4 weeks -20°C; ≤ 8 months -80°C; ≤ 5 F/T cycles |
Biomarker overview
| Test name | Matrix | Platform / methodology | Intended use |
|---|---|---|---|
| Phosphorylated Tau 217 (pTau-217) | Plasma | High-sensitivity automated immunoassay platforms | LDT for clinical use & clinical trial research |
| Neurofilament light chain (Nf-L) | Plasma or Serum | Automated immunoassay platform | LDT for clinical use & clinical trial research |
| Glial fibrillary acidic protein (GFAP) | Plasma | Automated immunoassay platform | LDT for clinical use & clinical trial research |
| Amyloidβ 42/40 (Aβ42/40) | Plasma | High-sensitivity automated immunoassay platform | Clinical trial research |
| Total Tau, amyloidβ 42/40 (Aβ42/40), pTau-181, and Nf-L | CSF | Automated immunoassay platforms | IVD & LDTs for clinical use & clinical trial research |
Analytical and clinical performance were determined per CLSI guidelines.
Clinical positioning
pTau-217 is presented as the plasma biomarker with reported amyloid PET-aligned performance, while Nf-L, GFAP, and Aβ42/40 add broader neurodegenerative and differential-diagnosis context.
Amyloid pathology insight
Accessible blood testing
Use with clinician guidance
Use results within the full clinical picture and consider CSF or PET follow-up when additional clarity is needed.
Evidence Summary
Additional biomarker notes and support details
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Educational reference for clinician conversations
GFAP
GFAP is a biomarker of astrocyte activation, which occurs in response to many CNS pathologies including stroke, TBI, and neurodegenerative diseases including AD; GFAP provides valuable information for differential diagnosis.
| Metric | Value |
|---|---|
| Precision | ≤ 3% intra-laboratory |
| AUC | 0.96 (Aβ PET+ vs HC) |
| Age reference range (ng/L) | < 60: ≤ 48.2 60 - 69: ≤ 64.9 ≥ 70: ≤ 90.7 |
| Stability | ≤ 1 week room temp ≤ 1 week 4°C ≤ 3 weeks -20°C ≤ 6 months -80°C ≤ 4 F/T cycles |
Nf-L
Nf-L is a nonspecific biomarker for axonal degeneration; elevated Nf-L levels are associated with a range of neurological disorders including AD, ALS, MS, FTD, and TBI.
| Metric | Value |
|---|---|
| AMR (ng/L) | 2.0 - 741.6 |
| Precision | ≤ 10% intra-laboratory |
| Accuracy | 95% |
| Age reference range (ng/L) | 20 - 29: ≤ 8.4 30 - 39: ≤ 11.4 40 - 49: ≤ 15.4 50 - 59: ≤ 20.8 60 - 69: ≤ 28.0 70 - 79: ≤ 37.9 ≥ 80: ≤ 51.2 |
| Stability | ≤ 1 week room temp ≤ 1 week 4°C ≤ 1 week -20°C ≤ 6 months -80°C ≤ 5 F/T cycles |
Aβ42/40
The ratio of Aβ42 to Aβ40 is a biomarker of amyloid plaque accumulation in the brain. A lower Aβ42/40 is indicative of AD, as Aβ42 is more prone to aggregation into plaques; normalization with Aβ40 helps ameliorate inter-individual differences in amyloid levels and increases diagnostic accuracy.
CSF Aβ42/40 assays have also been used as amyloid-focused diagnostic aids in appropriate clinical settings.
Aβ42/40 supports amyloid-focused assessment when used alongside other biomarkers and clinical findings.
ALZ Blood Test provider support
ALZ Blood Test helps clinics and care teams offer accessible, science-driven Alzheimer's biomarker information. We support provider onboarding, program information, educational materials, and operational guidance so practices can bring biomarker context into evaluation and next-step decisions.
For provider support, onboarding questions, or educational materials, contact the ALZ Blood Test team directly.
1 (844) 259-8378
support@alzbloodtest.com
alzbloodtest.com
References
- 2022 Alzheimer's disease facts and figures. Alzheimers Dement. 2022 Apr;18(4):700-789. doi: 10.1002/alz.12638. Epub 2022 Mar 14. PMID: 35289055.
- Hansson O, Edelmayer RM, Boxer AL, Carrillo MC, Mielke MM, Rabinovici GD, Salloway S, Sperling R, Zetterberg H, Teunissen CE. The Alzheimer's Association appropriate use recommendations for blood biomarkers in Alzheimer's disease. Alzheimers Dement. 2022 Dec;18(12):2669-2686. doi: 10.1002/alz.12756. Epub 2022 Jul 31. PMID: 35908251; PMCID: PMC10087669.