Lower Vitamin D Levels Are Associated With Higher Systemic Lupus Erythematosus Activity, But Not Predictive Of Disease Flare-Up

Objectives: Growing evidence suggests that vitamin D plays a key role in the pathogenesis and progression of autoimmune diseases, including systemic lupus erythematosus (SLE). Recent studies have found an association between lower serum 25-hydroxyvitamin D (25(OH) D) levels and higher SLE activity. We studied the relationship between 25(OH) D levels and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score, and we assessed for the first time the role of vitamin D in predicting SLE flare-ups.Methods: Serum 25(OH) D levels were measured in 170 patients with SLE who were prospectively followed up for 6 months (Plaquenil LUpus Systemic study, ClinicalTrials.gov number NCT00413361).Results: The mean SLEDAI score was 2.03 +/- 2.43 and 12.3% patients had active disease (SLEDAI >= 6). The mean 25(OH) D level was 20.6 +/- 9.8 ng/mL. Deficiency (25(OH) D <10 ng/mL) was observed in 27 (15.9%), insufficiency (10 <= 25(OH) D<30) in 112 (65.9%) and optimal vitamin D status (25(OH) D >= 30) in 31 (18.2%) patients. In multivariate analysis, female gender (p=0.018), absence of defined antiphospholipid syndrome (p=0.002) and higher creatinine clearance (p=0.004) were predictive of lower 25(OH) D levels. In multivariate analysis, lower 25(OH) D levels were associated with high SLE activity (p=0.02). Relapse-free survival rate was not statistically different according to the vitamin D status during the 6-month follow-up (p=0.22).Conclusions: We found a low vitamin D status in the majority of patients with SLE, and a modest association between lower 25(OH) D levels and high disease activity. There was no association between baseline 25(OH) D levels and relapse-free survival rate.