The US Food and Drug Administration cleared a blood-based diagnostic test for Alzheimer's disease for use in primary care on Tuesday, expanding early detection beyond memory clinics and specialist centres. The assay measures plasma phosphorylated tau (p-tau217).

The clearance builds on the FDA's May 2025 authorization of the first blood test for Alzheimer's, which was limited to specialist settings and patients already undergoing cognitive evaluation. The new decision extends screening to general practitioners, who see the majority of older patients reporting memory problems.

The test detects biomarkers associated with amyloid plaques, a hallmark of Alzheimer's pathology, and offers an alternative to costly PET scans and invasive spinal fluid analysis. Manufacturers including Roche, Fujirebio and Quest Diagnostics have pursued regulatory clearance for plasma assays, citing validation data showing accuracy above 90 percent against established methods.

The Alzheimer's Association welcomed the move as a route to earlier treatment with recently approved anti-amyloid drugs such as lecanemab and donanemab. Those therapies work best when started early, making timely diagnosis critical.

Neurologists cautioned that positive results still require confirmatory evaluation to avoid overdiagnosis. Roughly seven million Americans live with Alzheimer's, according to the Alzheimer's Association, a figure projected to nearly double by 2050 as the population ages. Broader testing in primary care could reshape how the disease is identified and managed across health systems.