Vitamin D serum level, disease activity and functional ability in different rheumatic patients.

Background: The aim of the study was to determine the serum vitamin D levels in patients with psoriatic arthritis (PsA) and compare it with patients with rheumatoid arthritis (RA) and with osteoarthritis (OA), as well as to explore the relationship of the vitamin D level with indices of disease activity and functional ability in a real-life setting in a South-European country.
Methods: In a cross-sectional study, 120 adult patients with established diagnosis of PsA, RA and OA were consecutively enrolled. Serum 25-hydroxyvitamin D and intact parathyroid hormone were determined. Parameters of disease activity and functional ability were obtained using standard instruments.
Results: Serum vitamin D insufficiency (≤ 75 nmol/L) was found in 74% of patients with PsA, 94% patients with RA and 97% of patients with OA, whereas vitamin D deficiency (≤ 25 nmol/L) was found in 13% of patients with PsA, 39% of patients with RA and in 38% of patients with OA. Compared with RA, patients with PsA had significantly higher serum vitamin D (P = 0.002), and when controlling for age and gender, their serum vitamin D level was significantly associated with disease activity and functional activity.
Conclusions: In the group of rheumatic patients, a high prevalence of serum vitamin D insufficiency/deficiency was found regardless of the type of arthritis. Patients with PsA might have higher levels of vitamin D than patients with RA, and this was associated with disease activity and functional ability. The results of this study indicate that prophylactic supplementation with vitamin D might be recommended for all rheumatic patients.