Background Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that mainly affects women of childbearing age. Recent studies suggest a high prevalence of vitamin D insufficiency and deficiency in patients with SLE. Inadequate levels of vitamin D could determinate not only skeletal problems but also a potentiation of autoimmune activity in SLE.

Objectives The purpose of this study was to determine the prevalence of vitamin D insufficiency and deficiency in SLE patients attended in a tertiary care center.

Methods Consecutive patients with SLE seen in the Lupus Clinic of a Rheumatology Service belonging to a high complexity center in the Spanish Public Health System were included. Patients had to fulfill the 1997 ACR criteria for the classification of SLE. Different epidemiological, clinical, laboratory and serological variables were recorded. Levels of vitamin D and PTH, as well as serum levels of calcium, phosphorus, and alkaline phosphatase were systematically determined in all patients serum. Serum vitamin D levels at 25 nmol/L and 75 nmol/L were the cut-off values for vitamin D deficiency and vitamin D insufficiency, respectively. The local ethical committee authorized the study. Descriptive statistics was used to present the results; chi-square test, Student t test, and Mann-Whitney U test were used to establish statistical significance. A p<0.05 was considered significant. Statistical analyses were performed by using Stata v12.0.

Results One hundred and twenty patients were included, with a mean age of 51 years. Eighty-nine percent were women and 89% were caucasian. The average time of disease evolution was 13 years. Seventy-six percent of patients were taking hydroxychloroquine, 42% were taking glucocorticoids, and 37% of them were taking calcium plus vitamin D supplements.

Nine percent of patients had vitamin D deficiency and 56% had vitamin D insufficiency. Elevated levels of PTH were detected in 18% of patients with vitamin D insufficiency and in 45% of patients with vitamin D deficiency. There were no statistically significant differences between them and patients with optimal levels of vitamin D. Likewise, no statistically significant association was observed between suboptimal vitamin D levels and skin involvement, photosensitivity, use of photoprotection, use of glucocorticoids, use of antimalarial or use of anticonvulsants.

Conclusions Despite taking vitamin D and calcium supplements, vitamin D deficiency and insufficiency are common among SLE patients. Therefore, it might be advisable to monitor serum vitamin D levels in order to adjust the dose of vitamin D prescribed.

Disclosure of Interest None declared