Serum vitamin D level and disease activity in patients with recent onset rheumatoid arthritis

Rheumatoid Arthritis (RA) is one of the most prevalent autoimmune diseases. Due to the significance of the relationship between serum vitamin D levels and autoimmune diseases, this study aimed to determine the relationship between serum vitamin D level and the severity of disease activity in patients with newly diagnosed RA.

This cross-sectional study was conducted on 66 patients meeting the American College of Rheumatology - European League Against Rheumatism classification criteria for RA. It was performed in 2012 using simple sampling. The disease activity was measured based on Disease Activity Score of 28 joints - erythrocyte sedimentation rate (DAS28-ESR) and serum 25-OH vitamin D (25(OH)D) levels using the chemiluminescent immunoassay method. In addition, the levels of ESR and C-reactive protein (CRP), the duration of morning stiffness, and the number of joints with tenderness and swollen were calculated as well. The data were analyzed using the Pearson correlation coefficient.

In this study, 10 patients were male (15.2%) and 56 were female (84.8%). The average age of the participants was 45.2 ± 15.3 years. The average level of 25(OH)D in the patients' serum was 30.5 ± 28.9 ng/mL and the mean DAS28-ESR was 5.6 ± 1.1. The correlation coefficient showed that there was an inverse relationship between 25(OH)D and DAS28-ESR, the number of tender and swollen joints, global patient assessment and duration of morning stiffness (P < 0.01). However, the average 25(OH)D level was not related to ESR (P = 0.779) and CRP (P = 0.269).

The results of this analysis indicated that patients with more active RA have a lower serum vitamin D level.