Blood-based biomarkers move from research to clinical workflow
Plasma p-tau217 assays are being adopted as a triage step before PET or CSF confirmation in specialty memory clinics.
A blood draw is becoming the entry point to the Alzheimer's diagnostic pathway — not the endpoint.
For two decades, confirming Alzheimer's pathology required either a lumbar puncture or an amyloid PET scan — both expensive, both gated by specialist access. Plasma assays measuring phosphorylated tau (most prominently p-tau217) have changed the calculus. Several commercial tests now report performance comparable to CSF in symptomatic patients, and at a fraction of the cost.
The practical shift inside memory clinics is sequencing. Where previously a clinician ordered PET or CSF as a confirmatory test, plasma is increasingly the first step. Negative results may end the workup; positive results trigger confirmation imaging or CSF where required by payor or treatment-eligibility criteria.
Two things to watch:
- Whether primary care adopts the same sequencing, or whether it remains a specialty-clinic phenomenon.
- How payors treat plasma testing — coverage today is uneven, and out-of-pocket costs vary widely.
Key sources
- FDA in vitro diagnostic clearances for plasma Alzheimer's biomarkers
- Plasma p-tau217 assay technical disclosures (Quest, Labcorp, C2N, Roche)
- AAIC plasma biomarker validation and real-world performance studies