Fourth, building on recent progress, we propose that serum PF4 levels in the AD spectrum should be measured along with Aβ40, Aβ42, total and phosphorylated tau proteins, and even tau217 and tau181, because the latter two represent early, sensitive biomarkers for the identification of an AD-related high-risk population [29–35]. The gene discussed is MAPT; the disease is Alzheimer disease.