Serum concentrations of 25-OH vitamin D in patients with systemic lupus erythematosus (SLE) are inversely related to disease activity: is it time to routinely supplement patients with SLE with vitamin D?

Background Low serum vitamin D concentrations have been reported in several autoimmune disorders. Objective To assess whether low serum vitamin D concentrations are related to disease activity of patients with systemic lupus erythematosus (SLE). Methods 378 patients from several European and Israeli cohorts were pooled and their disease activity was measured by two different methods: 278 patients had SLE disease activity-2000 (SLEDAI-2K) scores and 100 patients had European Consensus Lupus Activity Measurement (ECLAM) scores. In order to combine the two systems the scores were converted into standardised values (z-scores), enabling univariate summary statistics for the two variables (SLEDAI-2K and ECLAM). The commercial kit, LIAISON 25-OH vitamin D assay (310900-Diasorin) was used to measure serum concentration of 25-OH vitamin D in 378 patients with SLE. Results A significant negative correlation was demonstrated between the serum concentration of vitamin D and the standardised values (z-scores) of disease activity scores as measured by the SLEDAI-2K and ECLAM scales (Pearson's correlation coefficient r = -0.12, p = 0.018). Conclusions In a cohort of patients with SLE originating from Israel and Europe vitamin D serum concentrations were found to be inversely related to disease activity.