Doctors Can Now Spot Alzheimer's With a Simple Blood Draw, Even at 40

Keypoints:

• The FDA cleared two new Alzheimer's blood tests in August 2026, bringing the total to four
• C2N Diagnostics' PrecivityAD2 is cleared for symptomatic adults as young as 40
• Roche's Elecsys pTau217, developed with Eli Lilly, targets adults 55 and older
• Roche's test is the first single-biomarker test that can both rule in and rule out amyloid pathology
• An estimated 75% of people living with dementia remain undiagnosed

Doctors evaluating a patient for Alzheimer's now have two new tools that don't require a brain scan. The FDA cleared C2N Diagnostics' PrecivityAD2 on August 20, followed four days later by Roche and Eli Lilly's Elecsys pTau217, bringing the total number of FDA-cleared Alzheimer's blood tests to four in the span of about fifteen months.

The two tests fill different gaps. PrecivityAD2 is the first cleared for symptomatic adults as young as 40, using a combination of amyloid and tau biomarkers to broaden who can get tested well before typical retirement age. 

Roche's Elecsys pTau217 covers adults 55 and older and stands out for a narrower technical reason: it's the first single-biomarker blood test cleared to both rule in and rule out amyloid pathology using the same validated cutoffs, whether a patient sees a primary care doctor or a specialist.

Neither test works alone. Both require an existing cognitive or clinical evaluation first, and neither is approved as a population-level screening tool for people without symptoms, a distinction doctors are being urged to keep front and center as the tests roll out. 

Roche's version runs on existing lab instruments with an 18-minute turnaround, and Labcorp and Quest Diagnostics have both announced plans to offer it, with Quest targeting the fourth quarter of 2026 for launch.

The bigger number sitting behind all of this is the one nobody's solved yet. Roche estimates 75% of people living with dementia remain undiagnosed, often going years without a clear answer after symptoms first appear. A blood draw won't close that gap by itself, but four cleared tests in just over a year marks a sharp shift from a field that had zero blood-based options before May 2025.