Analyzing the STA and t-tau ratio levels in the cohort according to each of the six different Braak stages ( n = 6 Braak stage 0; n = 4 (I); n = 4 (II); n = 8 (III); n = 5 (IV); n = 9 (V); n = 31 (VI)) highlights a sharp decrease in the ratio between Braak stages III and IV, suggesting a pathology-dependent increase in the amount of soluble tau in human CSF once affected individuals reach this disease stage. As above, the center of the box plot indicates the median, the box boundaries indicate the 25th and 75th percentiles, and the whiskers indicate the furthest value 1.5 times the IQR. The P values correspond to post hoc pairwise MannWhitney U -tests with FDR adjustment, after a significant overall KruskalWallis rank-sum test (chi-squared = 31.6, d.f. = 6, P = 1.9 10 -5 ).
