Diagnosis of progressive supranuclear palsy: can measurement of tau forms help?

Abstract

Recently, a new assay for the differential diagnosis of progressive supranuclear palsy (PSP) was proposed. It was shown that the ratio of 33/55 kDa tau forms in cerebrospinal fluid (CSF) was specifically reduced in PSP CSF. We aimed to reproduce these results, but were not able to detect the tau forms in CSF. We demonstrate that i) CSF total tau levels are too low to be detected by the published protocol, and ii) the described 33 and 55 kDa bands are likely the heavy and light chains of IgG used in the assay. We conclude that more sensitive techniques are needed to measure tau forms in CSF.