MAPT and Alzheimer disease: Cut-off points to define positivity for AD: Aβ1−42 < 638 pg/mL; total (t)-tau > 404 pg/mL; p-tau 181 > 52.1 pg/mL; t-tau/ Aβ42 > 0.784; Aβ1−42/Aβ1−40 < 0.068.