MAPT and Alzheimer disease: In patients with a non-AD diagnosis and ADNC data (n = 83, P-tau181 data were missing in 4 of these), Aβ42/Aβ40 was positive in 2 of 68 patients with ADNC none-low (97% specificity), and P-tau/Aβ42 was positive in 4 of 64 patients with ADNC none-low (94% specificity).