MAPT and Alzheimer disease: However, in this study, no single biomarker or combination of biomarkers was able to distinguish aMCI from AD, in contrast to previous findings suggesting that the combination of Aβ1-42 and tau protein could be used to differentiate AD in the prodromal and dementia phases [22] and that plasma levels of p-Tau181 could be used to categorize disease severity in patients with early-stage AD [32].