Alzheimer’s Blood Test Brings Early Detection to Primary Care
Roche’s Elecsys pTau181 test may help family doctors rule out Alzheimer’s-related brain changes before specialist referral
The FDA has cleared Roche’s Elecsys pTau181 as the first blood-based biomarker test for Alzheimer’s usable in primary care, showing a 97.9% negative predictive value in ruling out amyloid pathology in older adults with cognitive decline.
Study Details:
The Elecsys pTau181 test measures phosphorylated tau 181 (p-tau181) in plasma, a protein fragment linked to amyloid plaque buildup and tau aggregation two hallmarks of Alzheimer’s disease. The FDA clearance enables its use among patients 55 years and older presenting with memory issues or cognitive symptoms in primary care settings, helping rule out Alzheimer’s-related causes early in the diagnostic process.
Methodology:
The clearance was based on a multicenter, non-interventional study involving 312 participants reflective of real-world primary care populations. The test achieved a 97.9% negative predictive value, meaning a negative result reliably ruled out Alzheimer’s pathology.
Key Findings:
The Elecsys pTau181 test helps triage patients efficiently before expensive or invasive tests like PET scans or cerebrospinal fluid analyses.
It meets the Alzheimer’s Association’s biomarker guidelines, which recommend blood tests with ≥90% sensitivity and ≥75% specificity for initial screening.
This approval follows the May 2025 FDA clearance of Lumipulse G pTau217/β-Amyloid 1-42, which is limited to specialized care, whereas Elecsys pTau181 opens access at the primary care level.
Implications for Practice:
For primary care physicians, this test represents a major step toward earlier identification and streamlined referral of Alzheimer’s patients. It may reduce diagnostic delays, helping neurologists focus on confirmed or high-probability cases suitable for newer treatments such as lecanemab (Leqembi) and donanemab (Kisunla).
For patients and families, a simple blood draw may now provide reassurance or early direction, helping initiate lifestyle adjustments or treatment discussions much sooner