Diagnostic Biomarkers of Amyloid and Tau Pathology in Alzheimer's Disease: An Overview of Tests for Clinical Practice in the United States and Europe.

Amyloid and tau biomarkers for Alzheimer's disease are widely recognized diagnostic tools for the identification of Alzheimer's disease pathology antemortem and are recommended by the most recent clinical and research guidelines. Approved biomarkers include positron emission tomography (PET)- and fluid-based markers derived from cerebrospinal fluid and, more recently, plasma. These biomarkers are still infrequently used in clinical practice, potentially due to challenges in access to and understanding of individual assay information and methodology. We provide an overview of the diagnostic biomarkers for amyloid and tau pathology that are currently available in the US and/or EU for clinical use. Available performance data from both labels/instructions for use and the scientific literature (with focus on autopsy or PET as standard of truth) are summarized to help healthcare providers navigate the biomarker landscape. All available PET amyloid and tau biomarkers demonstrate high accuracy in identifying amyloid and tau Alzheimer's disease pathology, respectively, at autopsy. Among cerebrospinal fluid biomarkers, all showed accurate prediction of Alzheimer's disease pathology, either based on autopsy or PET findings; greater accuracy was evident for concentration ratios (Aß42/40 or P-tau181/Aß42) versus individual biomarker concentrations. Among plasma biomarkers, Aß42/40 and P-tau181 demonstrated high agreement with PET findings. Overall, we conclude that commercially available PET, cerebrospinal fluid and plasma assays accurately identify Alzheimer's disease amyloid and tau pathology. The recent development of fully automated tests for fluid-based biomarkers improves test reliability. The continued development of plasma biomarkers holds promise for the future management of patients with Alzheimer's disease.