Firstly, we used an exploratory IP‐MS approach on AD and control TBS‐soluble fractions, showing that TBS‐soluble fraction does indeed reflect CSF in terms of tau phosphorylation; mono‐phosphorylated tryptic peptides containing p‐tau181, p‐tau217 and p‐tau231 were among the most prominent species identified. Here, MAPT is linked to Alzheimer disease.