The Biomarker Profile of Alzheimer's Disease for Disease-Modifying Treatment Eligibility: Questions and Debates

Alzheimer's disease (AD) is the most common cause of cognitive decline; currently, anti-amyloid monoclonal antibodies are available for clinical use as disease-modifying treatments, while many other substances are being tested in clinical trials. Molecular biomarkers for AD have been studied for more than two decades, and various guidelines and diagnostic recommendations have been published. However, there are still questions and controversies about the biomarker profile needed to confirm AD and the eligibility for such established treatments and clinical trials. Is amyloid positivity sufficient for eligibility, or is a biomarker for tau biochemistry/pathology also needed? What is the role of hybrid ratios combining amyloid and tau? Should we rely on plasma biomarkers alone? This review aimed to describe and discuss such questions and controversies.