MAPT and amyotrophic lateral sclerosis: Most interestingly, in ALS, the strong correlations between blood p-tau 181 and blood troponin T, a marker of striated and myocardial muscular damage which is usually elevated in ALS (together with other muscular markers)14–16, the lack of correlation between CSF and serum p-tau 181 levels9,10,12, and the higher serum marker levels in LMN-predominant ALS10, indicate that a substantial fraction of blood p-tau 181 in ALS is probably derived from a peripheral source.