Abstract

IntroductionModification of CSF tau phosphorylation in AD remains controversial since total-tau and phospho-tau levels measured by immunoassays are highly correlated.\n\nMethodsStoichiometry of phosphorylation of CSF tau was monitored on five sites by mass spectrometry. We compared 50 participants with AD at mild to moderate stages, others tauopathies and controls then confirmed our results in a cohort of 86 participants cognitively normal or with mild cognitive impairment and stratified according to amyloid-{beta} status.\n\nResultsChanges in tau phosphorylation rates were observed in AD participants but not in other tauopathies. T181 appeared slightly hyperphosphorylated in AD. In comparison, T217 phosphorylation, was considerably modified. We demonstrated T217 hyperphosphorylation occurred systematically in amyloid positive participants even at preclinical stage (AUC 0.999). T217 phosphorylation change specificity overpasses other phosphorylated tau sites investigated in this study, but also CSF total-tau and p-tau levels.\n\nDiscussionCSF T217 hyperphosphorylation defines a specific tauopathy status concomitant with {beta}-amyloidosis.