MAPT and Alzheimer disease: When combining each of these known serum biomarkers with serum p75NTR-ECD, the AUC value, sensitivity and specificity were all elevated compared with each alone (Supplementary Table 3; Figure 3a and b), indicating that serum p75NTR-ECD has a potential diagnostic value for AD when applied alone or in combination with serum Aβ and tau.