Guan SY, Cai HY, Wang P, et al. - Researchers conducted this systematic review and meta-analysis to thoroughly investigate the status of 25-hydroxyvitamin D (25(OH)D) in patients with systemic lupus erythematosus (SLE) and assess its relationship to SLE risk and severity of the disease. In the databases of Pubmed, Embase and Cochrane Library, literature on the 25(OH)D status and its associations with SLE were searched. The meta-analysis included 19 articles. Compared with healthy controls, 25(OH)D levels in SLE patients are significantly lower, influenced by disease activity, ethnicity, seasons and vitamin D supplement; regardless of age, diseases duration and therapy of corticosteroid or immunosuppressive or neither, 25(OH)D levels in SLE patients are significantly reduced; vitamin D deficiency, insufficiency, and sufficiency could significantly increase, decrease slightly, and decrease SLE risk significantly, respectively. Circulating levels of 25(OH)D were inversely linked to Systemic Lupus Erythematosus Disease Activity Index.