Blood Tests for Alzheimer Disease—When the Holy Grail Is Found

In this issue of JAMA Neurology, Malek-Ahmadi and colleagues present a meta-analysis of 17 studies, conducted over just the last 5 years, of the ability of plasma phosphorylated tau 217 (p-tau217) to distinguish groups of individuals without cognitive impairment who test positive on traditional Alzheimer disease (AD) biomarkers from those who test negative. They conclude that plasma p-tau217 is a powerful tool to differentiate these groups, with consistent high effect sizes and areas under the receiver operating characteristic curve.