25-Hydroxyvitamin D levels in acute monosymptomatic optic neuritis: relation to clinical severity, paraclinical findings and risk of multiple sclerosis.

Optic neuritis (ON) is a common first symptom of MS and only few studies have thus far investigated vitamin D at this early stage of MS. The objectives of the study were to examine total 25-hydroxyvitamin D levels (25HVITDL) in patients in acute (A) ON and to determine whether 25HVITD levels in AON (1) predict risk of RRMS and (2) are associated with visual tests of ON severity. A cross-sectional study was conducted of mean 25HVITDL differences between ON (n = 164) and MS (n = 948) patients and of prevalence of 25HVITDL deficiency (<50 nmol/L) in ON and MS (two-sample t test, χ (2) test). Associations between 25HVITDL and (1) clinical ON severity, (2) paraclinical findings suggestive of MS [logistic regression (LRA), Spearman correlation] and (3) hazard of MS development [Cox (C) RA] in ON patients were assessed. 25HVITDL were deseasonalized before analysis. The mean levels were 47.6 (ON) and 63.9 (MS) nmol/L (p < 0.0001), and a significantly higher prevalence of 25HVITD deficiency in ON (56 %; 35 %) (p < 0.0001), most pronounced in females, was shown. Associations were found between 25HVITDL and both CSF leukocyte count (ρ = -0.177, p = 0.028) and IgG index elevation (OR 0.980, p = 0.031). Forty-one ON patients developed MS during the study. Multivariate CRA showed no effect on hazard of MS (HR: 0.991, p 0.284). No association was found between 25HVITDL and visual tests (acuity, contrast vision) or OCT RNFL or GCL thickness. The study indicates a high prevalence of 25HVITD deficiency in AON. 25HVITDL was significantly associated with CSF leukocyte count, but not ON severity. The study indicates a possible role of vitamin D in the early stages of MS, but does not support the use of 25HVITDL as a predictor of MS development in acute ON.