MAPT and Alzheimer disease: By Spearman-Kärber analysis, the analytical sensitivity of the assay was roughly ~ 75 fM for synthetic AD-seeded K12CFh fibrils, and ~ 7.5 fM for both synthetic PiD-seeded K12CFh fibrils and spontaneously converted (tau KO mouse-seeded) fibrils, comparable to the analytical sensitivity of the previously published AD tau RT-QuIC [21].