MAPT and Alzheimer disease: Although the differences were modest, stronger correlations observed with PET would also prove consistent with findings showing that threonine 217 phosphorylation was considerably increased in AD as compared to threonine 1818,35 and with the preferential phosphorylation of tau at specific sites across the different stages of AD.16,36 In addition, by comparison to studies using p-tau181 measurements from commercial assays such as p-tau181Innotest and p-tau181Elecsys,37 larger effect sizes were seen when using p-tau181Lilly, p-tau217Lilly, and p-tau231ADx.