Tau protein seems not to be a useful routine clinical marker of axonal damage in multiple sclerosis

Background The descriptions of early axonal damage in patients with multiple sclerosis (MS) prompted the search of body fluid markers. However, the studies addressing this issue in MS present conflicting results. Aim To assess the levels of tau protein in patients with definite MS. Patients and methods Cerebrospinal fluid (CSF) samples from 50 patients with definite diagnosis of MS (33 F, 17 M; mean age: 33.6 years) and from 19 age-matched individuals without organic neurological diseases (11 F, 8 M), entered this study. With regard to the clinical course, the MS patients were classified as follows: 32 relapsing-remitting (RR); two secondary progressive (SP), and four primary progressive (PP). Twelve patients had clinical isolated syndromes (CIS). The mean duration was 36.1 months (range: 15 days to 20 years). Tau protein was measured in the CSF by double antibody sandwich ELISA. Results The median tau and the cut-off values of the controls were 104.9 and 175.3 pg/mL, respectively. We found that most MS patients presented normal values. In addition, the clinical features - course, duration, Expanded Disability Status Scale (EDSS) value, Poser index of progression, Multiple Sclerosis Severity Score - did not significantly influence the tau levels in the MS group. Conclusion Our study showed similar CSF tau concentrations in MS patients with different clinical characteristics. This suggests that tau protein does not seem to be a useful routine clinical marker of axonal damage.