HC, AD and svPPA groups showed plasma sEV 3/4R tau ratios of ~1, consistent with the balanced ratios of 3R and 4R tau described in physiological conditions and in AD tau aggregates31 (HC median 1.16, interquartile range (IQR) [0.99–1.28]; AD median 0.91, IQR [0.57–1.25]; svPPA median 1.00, IQR [0.98–1.11]) (Fig. 1a). Here, MAPT is linked to Alzheimer disease.