Alzheimer’s Association Backs High-Accuracy Blood Tests for Diagnosis

The Alzheimer’s Association issued its first clinical guidelines allowing certain blood biomarker tests to be used in place of positron-emission tomography (PET) scans and spinal fluid analyses for diagnosing Alzheimer’s disease in patients who already show cognitive impairment. Tests that demonstrate at least 90% sensitivity and 90% specificity may replace the more invasive and costly procedures, the non-profit said. Assays that reach 90% sensitivity but a lower 75% specificity can be used to triage patients, with positive results confirmed by standard imaging or cerebrospinal testing. The recommendations, published 29 July, aim to broaden access to diagnosis, particularly in regions where PET scanners and lumbar puncture facilities are scarce. The association reviewed nearly 50 studies but did not endorse individual assays, noting that performance varies widely across commercial offerings that track markers such as pTau217 and the Aβ42-to-Aβ40 ratio. Only one blood test for Alzheimer’s has been cleared by the U.S. Food and Drug Administration to date. Experts involved in drafting the guidance cautioned that blood tests are not yet reliable for monitoring amyloid levels once treatment begins and should not replace a full clinical evaluation. Nevertheless, they said the new framework could accelerate identification of eligible patients as recently approved disease-modifying drugs from Eisai, Biogen and Eli Lilly reach the market.