To estimate the prevalence of low serum vitamin D level (25[OH]D) in patients with rheumatoid arthritis (RA) compared with healthy controls, and to analyze the association between 25(OH)D and disease activity.
This retrospective analysis included 100 RA patients (85% women) and 100 controls, not on vitamin D supplements from January 2010 to December 2011 at a tertiary care center at the Department of Internal Medicine, King Abdulaziz University Hospital (KAUH), Jeddah, Kingdom of Saudi Arabia. Disease activity was measured using the disease activity score index (DAS28). According to the DAS28 score, RA patients were divided into 3 groups as high, moderate, and low disease activity. Patients' serum 25(OH)D was measured in a centralized laboratory.
The mean 25(OH)D in patients with RA was similar to the control group (32.3+/-14.4 nmol/L) versus (31.4+/-16.4 nmol/L) (p=0.41). Patients with high disease activity had the lowest 25(OH)D levels (18.25+/-8.3 nmol/L) compared with patients with moderate (35.13+/-15.2 nmol/L) and low (38.05+/-7.3 nmol/L) disease activity (p<0.001). Serum 25(OH)D was negatively correlated with DAS28, which was statistically significant (r= -0.42, p<0.0001).
Serum vitamin D levels in RA patients were similar to the healthy control group. However, significantly lower 25(OH)D values were found in patients who are poorly responding to treatment, and not in a state of disease remission.