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

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

Methodology: 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.