This study aims to measure the serum level of 25-hydroxyvitamin D₃ (25-OH-D₃) in 302 patients with rheumatoid arthritis (RA), studying the association to disease activity. Three hundred two RA patients underwent clinical examination and serological analysis. 25-Hydroxyvitamin D₃ was determined by high-performance liquid chromatography-tandem mass spectrometry. Vitamin D₃ deficiency defined as serum levels of 25-hydroxyvitamin D₃ below 50 nmol/l was detected in 101 RA patients (33.4 %). There was no significant correlation between the serum level of 25-hydroxyvitamin D₃ and Disease Activity Score 28 (DAS28) (3w) score. In a subpopulation of RA patients with very low serum level of 25-OH-D₃ (≤15 nmol/l) (n = 15), there were significant differences compared to patients with normal 25-OH-D3 (n = 200): higher percentage of patients with positive rheumatoid factor (100.0 versus 77.5 %; p = 0.05), higher CRP (28.7 versus 14.8 mg/l; p = 0.001), higher number of patients treated with at least three disease-modifying antirheumatic drugs (DMARDs) (40.0 versus 14.5 %; p = 0.02), higher number of patients with high disease activity DAS28 score of ≥5.1 (20.0 versus 4.5 %; p = 0.01), lower age (54.5 versus 64.0 years; p = 0.003) and shorter disease duration (5.1 versus 10.3 years; p = 0.06). Deficiency of 25-hydroxyvitamin D₃ was detected in 33.4 % of the RA patients. A subpopulation of patients with severe deficiency of vitamin D₃ serum level of ≤15 nmol/l was characterised by all being positive for rheumatoid factor, high percentage of patients with very high disease activity and high percentage of patients treated with at least three DMARDs.
Clinical Rheumatology, 2013, Vol 32, Issue 5, p. 629-633
Disease activity; Rheumatoid arthritis; Vitamin D (25-OH-D )