NEFL and supranuclear palsy, progressive, 1: Plasma sEV 3R/4R tau ratios correlated positively (r = 0.68, P < 0.0001) with plasma NfL levels in bvFTD, and negatively in the 4R tauopathy PSP (Fig. 1i,j (sEV r = −0.48, P = 0.001)).