Comparing AD to both DLB and FTD combined (non‐AD dementia group), p‐tau181 and the p‐tau181/Aβ42 ratio had the highest AUC values (Figure 2, 0.87 and 0.90, respectively), while all other markers and the multivariate set (Aβ40 × p‐tau181, and ratios Aβ42/GFAP and Aβ42/p‐tau181) had a maximum AUC of 0.72. This evidence concerns the gene GFAP and Alzheimer disease.