Several studies demonstrated the high value of plasma phosphorylated tau at threonine 181, 217, and 231 (p-tau181, p-tau217, p-tau231) in distinguishing patients with autopsy-confirmed Alzheimer disease (AD) from negative controls [3–7], with a diagnostic accuracy close to the one provided by CSF analysis [3–5]. This evidence concerns the gene MAPT and Alzheimer disease.