FDA Clears First Alzheimer's Blood Test for Patients as Young as 40

The US Food and Drug Administration has cleared C2N Diagnostics' PrecivityAD2 blood test for use in patients as young as 40 who show possible cognitive symptoms of Alzheimer's disease, making it the first FDA-cleared blood test for the condition in people this young. PrecivityAD2 uses mass spectrometry on a single blood draw to measure two Alzheimer's-linked proteins, amyloid and tau -- specifically plasma Ab42/40 and p-tau217/np-tau217 ratios -- and scores the result as negative, likely positive, or positive.

In a clinical validation study of 1,142 symptomatic adults, the test correctly identified 97.6% of positive biomarkers, with results remaining consistent even in patients with conditions such as chronic kidney disease and diabetes that can otherwise distort plasma amyloid readings. The test is intended for patients who already show cognitive decline, not for general health screening. Before blood tests like this became available, diagnosis relied on PET brain imaging or a lumbar puncture to sample cerebrospinal fluid.

PrecivityAD2 was developed by researchers led by Randall J. Bateman and David M. Holtzman at Washington University School of Medicine in St. Louis, and further developed and commercialized by C2N Diagnostics, a WashU startup that holds exclusive rights to the underlying technology. "The PrecivityAD2 test provides an accurate and reliable way to detect the presence of brain amyloid plaques associated with Alzheimer's disease pathology based on a single blood draw," Bateman said.

According to the Alzheimer's Association, about 7.4 million Americans aged 65 and older live with Alzheimer's disease, along with an estimated 200,000 more with younger-onset disease. PrecivityAD2 is the third Alzheimer's blood test to receive FDA clearance, according to Alzheimer's Drug Discovery Foundation chief executive Isobel Coleman, who noted that just over a year ago there were none.