The Significance of P-tau217 Noninferiority to Amyloid PET

One of the greatest challenges in Alzheimer disease (AD) diagnosis is not simply identifying pathology, but ensuring patients have access to the tools needed to detect it. While amyloid PET imaging and cerebrospinal fluid testing have transformed the ability to confirm underlying disease biology, their cost, availability, and procedural requirements continue to limit widespread implementation across many clinical settings.

At the 2026 Alzheimer's Association International Conference (AAIC), investigators reported that P-tau217 blood-based assays met prespecified criteria for noninferiority relative to amyloid PET quantitation in cognitively unimpaired individuals. Across independent cohorts, the assays demonstrated comparable positive predictive value-based agreement with amyloid PET, supporting the potential use of blood-based biomarkers as scalable tools for identifying AD pathology in individuals who may benefit from future prevention and intervention strategies.

In this episode of the NeurologyLive® Special Report, Yogesh Shah, MD, MPH, FAAFP, medical director of the Broadlawns Memory Clinic, site principal investigator for the University of Iowa Geriatric Workforce Empowerment Program, and board member of the Iowa Chapter of the Alzheimer's Association, discusses why these noninferiority findings are significant for the field. Shah explains how blood-based biomarkers could help overcome longstanding diagnostic barriers, improve access to care, and ultimately enable earlier identification of patients with underlying AD pathology.

Transcript edited for clarity.

Yogesh Shah, MD, MPH, FAAFP: This is very exciting. This is the field we've been waiting for. I've been involved in Alzheimer disease care for more than 25 years, and we've always hoped for the day when a simple blood test performed in a regular clinic could provide information comparable to what we obtain through amyloid PET imaging or lumbar puncture.

If a blood test performed properly in the right laboratory can provide information that is as close as, or not inferior to, amyloid PET or cerebrospinal fluid testing, then it truly becomes a game changer.

In many parts of the United States, access to amyloid PET imaging remains limited. Even in areas where PET imaging is available, it is expensive. Amyloid PET scans can cost several thousand dollars, and obtaining insurance approval often requires significant time and effort from both patients and clinical staff.

Lumbar puncture presents similar challenges. While it is a valuable diagnostic tool and can be performed in many centers, it still requires a procedure, scheduling, additional resources, and carries the possibility of complications. Certain patients, such as those taking anticoagulants, may not be ideal candidates for lumbar puncture.

That's why these findings are so important. The demonstration of noninferiority for P-tau217, and potentially other future blood-based biomarkers, has the potential to make AD diagnosis much more accessible. It could democratize diagnosis by reducing barriers related to geography, cost, and healthcare access.

Many patients delay evaluation because of financial concerns or other social determinants of health. A blood test can be performed much more easily and in many more settings. In clinics like mine in Des Moines, we even have a mobile memory clinic, and our goal is to bring testing directly into the community rather than requiring patients to come to us.

I believe the future will allow us to identify many more individuals with AD and intervene earlier. Unfortunately, a substantial proportion of Americans with AD remain undiagnosed, even after symptoms develop. The gap is even larger among those with mild cognitive impairment, where many individuals never receive a formal diagnosis.

We still have a long way to go, but I am hopeful that P-tau217 and other blood-based biomarkers will make Alzheimer disease diagnosis much easier, more accessible, and ultimately more effective.

This conference coverage information is produced independently by Neurology Live and supported by Eli Lilly and Company who has no direct influence on the content itself.