MAPT and Alzheimer disease: Figure 4 shows the ROC curve of saliva components in the diagnosis of AD. The results were as follows: the areas under the curve (AUC) of salivary Aβ40, Aβ42, t-tau, and p-tau alone to diagnose AD were 53.11% (p = 1.00) and 84.83% (p = 0.28), 50.50% (p = 0.23), and 58.38% (p = 0.31). The AUC of Aβ42/Aβ40 and p-tau/t-tau combined to diagnose AD were 64.77% and 63.44%, respectively. Among them, the AUC of 4 biomarkers combined in diagnosis of AD was the largest, equal to 92.11% (p = 0.000).