Can the integration of blood-based biomarkers into Alzheimer's disease diagnosis revolutionize the field?

Abstract

INTRODUCTION Alzheimer's disease (AD) is a clinical-biological entity in which pathophysiological changes precede symptoms by years. Biomarkers are essential for early and accurate diagnosis, particularly in the era of disease-modifying therapies requiring biological confirmation. Cerebrospinal fluid (CSF) and amyloid positron emission tomography (amyloid-PET) are the reference standards, but increasing attention is devoted to blood-based biomarkers (BBMs) due to their scalability and cost-effectiveness. AREAS COVERED In this critical perspective, the authors critically appraise the current evidence supporting plasma phosphorylated tau at threonine 217 (p-tau217) as the leading BBM for AD. They also discuss its analytical performance, biological rationale, and diagnostic accuracy across the AD continuum, its relationship with established CSF, PET, and neuropathological biomarkers, its potential role in identifying patients eligible for disease-modifying therapies, and the main clinical and biological factors influencing its interpretation. Finally, they highlight current limitations, unresolved challenges, and give their future perspectives for the integration of plasma biomarkers into routine clinical practice. EXPERT OPINION BBMs are expected to reshape AD diagnostics. A stepwise approach, using plasma biomarkers as first-line tests followed by confirmatory CSF or PET, is currently the most feasible strategy. Ultimately, highly specific, brain-derived tau biomarkers may enable BBMs to replace CSF biomarkers.