Blood phosphorylated Tau181 reliably differentiates amyloid‐positive from amyloid‐negative subjects in the Alzheimer's disease continuum: A systematic review and meta‐analysis

INTRODUCTION: Blood-based biomarkers seem promising for the diagnosis of Alzheimer's disease (AD). METHODS: We performed a systematic review and meta-analysis on the potential of blood phosphorylated Tau181 (p-tau181) to differentiate amyloid-positive (A+) and amyloid-negative (A−) subjects. Two meta-analyses were conducted, showing the mean p-tau values in blood and cerebrospinal fluid (CSF) in the A+ and A− group, and the second comparing the mean p-tau concentrations in blood and CSF among A+ versus A- participants, by laboratory assessment method. RESULTS: Eighteen studies (2764 A+ and 5646 A− subjects) were included. The single-group meta-analysis showed mean higher blood p-tau181 values in the A+ than in the A− group. In the head-to-head meta-analysis, blood p-tau reliably differentiated A+ patients from A− participants. DISCUSSION: Regardless of the laboratory technique, blood p-tau181 reliably differentiates A+ and A− subjects. Therefore, it might have important applications for early diagnosis and inclusion in clinical trials for AD patients.