Objectives: Hypovitaminosis D is common in the general population. Many studies that have been conducted to show the association between vitamin D deficiency and systemic lupus erythematosus (SLE) reveal that deficiencies in vitamin D are common in this group of patients. Our aim was to study the relationship between 25(OH)D and disease activity in patients with SLE.
Methods: Retrospective cohort study of patients with SLE who were followed up at King Abdulaziz University Hospital, Jeddah, from January 2007 to November 2010. Demographic and clinical data were recorded and the 25(OH)D levels of the patients were measured. Chi square tests, Student's t-test, ANOVA and Pearson tests were used for data analysis. ANOVA test was followed by Bonferroni correction. A p-value <0.05 was considered significant.
Results: Ninety-five patients with SLE were enrolled in the study. The levels of 25(OH)D were significantly lower in patients with active SLE (n=41; 43%) than in those with inactive disease (n=54; 57%; p=0.04). The mean (SD) levels were 22.3 (14) nmol/L for patients with active disease against 25.0 (14) nmol/L for patients with inactive SLE. No correlation was detected between 25(OH) D levels and disease activity score evaluated by SLEDAI-2K. By Pearson correlation, a significant negative correlation existed between 25(OH) D and anti ds-DNA (r=-0.38; p<0.001); a positive correlation existed between 25(OH)D levels and C4 (r=0.25; p=0.25). By chi square testing, azathioprine treatment (OR=3.5), low C4 (OR= 2.23), low C3 (OR=1.92), and active disease (OR=1.6) were associated with 25(OH)D deficiency in SLE patients.
Conclusion: Vitamin D deficiency is frequent in patients with SLE. Patients with SLE have a higher risk of developing 25(OH)D deficiency in the presence of low serum C3 and C4 levels, and high anti-dsDNA levels.
Keywords: 25(OH)D deficiency; Disease activity; Systemic lupus erythematosus; Vitamin D.