Plasma p‐tau181 and p‐tau181/Aβ42 showed the strongest performance (AUC 0.87 and 0.90, respectively) to discriminate AD from the group of non‐AD dementias (FTD Aβ– and DLB Aβ–).The multivariate model (chosen consistently across all group comparisons; ROC statistics shown in Table 3 compared to individual plasma biomarkers), comprising the pre‐calculated interaction between Aβ40 × p‐tau181, and ratios Aβ42/GFAP and Aβ42/p‐tau181, had significantly higher AUC values compared to the top performing individual biomarker; however, such differences in AUC diminished with increasing disease stage. This evidence concerns the gene GFAP and frontotemporal dementia.