The status of serum vitamin D in patients with rheumatoid arthritis and undifferentiated inflammatory arthritis compared with controls

Inadequate vitamin D may be involved in the pathogenesis and or progression of several disorders, including connective tissue diseases. To determine the status of vitamin D in different stages of inflammatory arthritis, the levels of vitamin D in established rheumatoid arthritis (RA) and undifferentiated inflammatory arthritis (UIA) were compared with controls. Patients with RA and UIA entered the study. Serum 25-hydroxyvitamin D (25-OHD) was measured by ELISA method, and concentrations less than 20 ng/ml were considered as deficient levels. In statistical analysis, the Mann-Whitney U test was used for comparing differences between groups and logistic regression analysis with calculation of adjusted odds ratio (OR) was used to determine the association between serum 25-OHD deficiency and disease condition. A total of 108 RA, 39 UIA, and 239 controls were studied. There were no significant differences in mean serum 25-OHD level and frequency of serum 25-OHD deficiency between RA and controls (37 ± 37.7 vs. 33.2 ± 28.6 ng/ml, P = 0.96). But the mean serum 25-OHD level in UIA was significantly lower than in the controls (25.1 ± 23.9 vs. 33.2 ± 28.6 ng ml, P = 0.04). A significant positive association was observed between serum 25-OHD deficiency and UIA (56.4% vs. 35.5%, OR = 2.34, 95% CI, 1.18-4.65, P = 0.021) which remained significant after adjustment for sex and age (adjusted OR = 2.24, 95% CI, 1.01-4.55, P = 0.026). Whereas the association between serum 25-OHD deficiency and RA did not reach statistical significance (40.7% vs. 35.5%, OR = 1.24, 95% CI, 0.78-1.99). These findings indicate higher serum vitamin D deficiency in patients with ongoing arthritis rather than established arthritis. Respecting to deleterious effects of vitamin D deficiency on immune system and progressive nature of UIA, a significant proportion of high risk UIA can be recognized by serum 25-OHD determination.