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.