Vitamin D is not useful as a biomarker for disease activity in rheumatoid arthritis

To determine whether there is an association between serum vitamin D levels and the Disease Activity Index in patients with rheumatoid arthritis (RA).

An analytical, retrospective, cross-sectional study was performed at the Hospital Luis Vernaza and Center for Rheumatology and Rehabilitation. We included 18 to 75-year-old patients with a diagnosis of RA according to the 2010 classification criteria, and with a 25-hydroxyvitamin D (25 [OH] D) test within the last 3 months. The activity of the disease was assessed with the 28-joint Disease Activity Score (DAS28) and C-reactive protein (CRP) as an acute-phase reactant. Spearman's rank correlation coefficient was used to establish association between the variables.

A total of 100 RA patients were studied. The mean vitamin D levels were 32.9 ± 11.5 ng/mL. In all, 45% showed insufficient 25 (OH) D and 55% had normal levels; no deficient vitamin D values were found. According to the DAS28-CRP, patients with low, moderate and high activity had an average vitamin D level of 30.4 ± 10.7, 31.9 ± 10.7, and 31.8 ± 12.1 ng/mL, respectively. There were no significant correlations between the disease activity and the serum vitamin D level (P=.60).

In our group of RA patients, there was no statistically significant correlation between the levels of vitamin D and the activity of the disease, nor were other determining variables associated with vitamin D levels.