Rate of hypovitaminosis D and association of plasma concentration of 25(OH)D with indicators of disease activity in patients with rheumatoid arthritis

Vitamin D deficiency is an important environmental risk factor that influences the prevalence and severity of several autoimmune diseases, including rheumatoid arthritis (RA). The aim of this study was to determine the incidence of vitamin D insufficiency and deficiency in patients with RA, to establish the relationship between serum vitamin D levels and indicators of disease activity. 156 patients with RA were included in the study, mean age 60.2 ± 13.9 years. Assessment of clinical status was performed, serum concentrations of rheumatoid factor (RF), C-reactive protein (CRP), total vitamin D (25(OH)D), antibodies to cyclic citrullinated peptide (ACCP) were determined. RA disease activity was evaluated using DAS28 (disease activity score), SDAI (Simplified Disease Activity Index) и CDAI (Clinical Disease Activity Index) scores. Average levels of 25(OH)D in the surveyed sample were 25.2 ± 13.2 ng/ml. The results of the study indicate a high prevalence of vitamin D deficiency in patients with RA. Normal indicators of vitamin D, its insufficiency and deficiency were observed in 47 (30.3 %), 45 (28.7 %) and 64 (40.7 %) patients, respectively. Low level of serum 25(OH)D was associated with higher indices of RA activity according to DAS28, SDAI and CDAI, as well as with greater tender joint count. Vitamin D should be prescribed as an adjunctive therapy in patients with active RA due to its potential immunomodulatory effect, as well as for the prevention and treatment of bone metabolism disorders.