MAPT and amyloidosis: Taken together, single and combined measures of Aβ42, Aβ42/40, t-tau and p-tau are shown as useful markers for amyloid and tau positivity and predictors for progression to AD or cognitive decline in independent studies [7, 13, 15, 20, 22, 25, 26, 31, 34, 38, 40, 60].