Fig. 3

Comparison of plasma tau or ptau181 between AD and healthy controls. Meta-analysis of studies comparing plasma tau (a) and ptau181 (b) levels between AD and healthy controls, detected by the Simoa method. In ptau181 studies, the study of O’connor et al. was a familial AD study; the average age in the study of Rodriguez et al. was considerably higher; the control cohort used in the study of Suarez-Calvet et al. comprised ‘middle-aged’ adults; the TRIAD cohort in Karikari et al. included young individuals, all of which may have contributed to the heterogeneity. AD, Alzheimer’s disease; SD, standard deviation; CI, confidence interval; WMD, weighted mean difference