Blood Test for Alzheimer's Gets Closer to Clinical Reality in Older Adults

Alzheimer's disease diagnosis has long relied on expensive, invasive, or limited-access tools like PET imaging and cerebrospinal fluid analysis. The emergence of accurate blood-based biomarkers (BBMs) is poised to change this, making diagnosis faster, cheaper, and more widely available — a development with enormous implications for aging populations worldwide.

This commentary, published in Age & Ageing, reviews the latest evidence on BBMs for Alzheimer's disease with a specific focus on older adults. The authors highlight plasma phosphorylated tau 217 (p-tau217) as the standout marker, demonstrating consistently strong performance for detecting amyloid pathology across multiple analytical platforms and diverse clinical cohorts.

A key contribution of this paper is its examination of how geriatric-specific factors complicate BBM interpretation. Frailty, chronic kidney disease, polypharmacy, and multimorbidity can all influence absolute biomarker concentrations. Importantly, however, the authors conclude that current evidence suggests p-tau217's diagnostic accuracy remains largely preserved in older populations when results are interpreted within appropriate clinical context. Frailty may also modify how underlying AD pathology manifests clinically, adding another layer of interpretive nuance.

The authors propose integrating BBMs into a Comprehensive Geriatric Assessment (CGA) framework — a holistic approach that accounts for functional status, comorbidities, and social factors alongside biological markers. This, they argue, is the most pragmatic path to accurate and equitable diagnosis in older adults.

Caveats include the commentary's reliance on existing literature rather than new primary data, and the authors' note that BBMs should currently be used only in symptomatic individuals presenting to specialist services. Widespread use in asymptomatic screening is not yet supported by evidence or guidelines.