RESUMEN
To investigate the possible association between serum 25[OH] vitamin D[3] concentration and the severity of disease in Iranian patients with multiple sclerosis [MS] and to compare this concentration with a matched control group. This was an analytical cross sectional study performed at Jondishapour Neurology Clinic in Tehran, Iran. Patients with relapsing- remitting MS were categorized by disease severity: mild [0 = Expanded Disability Status Scale [EDSS] = 3], moderate [3.5 = EDSS = 5.5], and severe [6 = EDSS]. Serum concentrations of 25[OH] vitamin D[3], calcium, phosphorus, magnesium, and parathyroid hormone were measured in 98 MS patients and 17 healthy age- and sex-matched controls. Fisher's exact, Kruskal-Wallis, Mann-Whitney U test, and independent t and Spearman rank correlation tests were used. Serum 25[OH] vitamin D[3] concentration was significantly lower in patients with MS, especially in the severe MS subgroup, compared with healthy controls [P=0.047]. There was a statistically significant inverse correlation between 25[OH] vitamin D[3] concentration and EDSS score [P=0.049,R=-0.168 by Spearman rank correlation test], which was observed in women only [P=0.044, R=-0.199]. Our findings not only further disclose the lower level of vitamin D in MS patients in comparison with healthy controls, but also support the association between vitamin D and disease severity in MS