The association between serum vitamin D Level and disease activity in Thai rheumatoid arthritis patients

Background: Serum vitamin D level was inversely associated with the risk of developing new onset rheumatoid arthritis (RA) and disease activity, but some conflicting results have been reported. Objective: To examine the serum vitamin D status in Thai RA patients and possible independent factors affecting serum 25 hydroxyvitamin vitamin D (25(OH)D) and the associations of serum 25(OH)D level and the disease activity and functional status in Thai RA patients. Methods: A cross-sectional study was performed in 239 Thai RA patients. The blood levels of 25(OH)D2 and D3 were measured by chemiluminescent immunoassay. Disease activity was assessed according to tender and swollen joint counts, erythrocyte sedimentation rate (ESR), visual analog scale for global patient assessment, Disease Activity Score-28 (DAS-28) and Thai Health Assessment Questionnaire (Thai HAQ). Result: The mean vitamin D level was 28.79ng/mL. There were no associations between 25(OH)D levels and number of tender and swollen joint counts, DAS-28 score, HAQ score or rheumatoid factor (RF) and/or anti-cyclic citrulinated peptide (CCP) positivity. After multivariated analysis, Bangkok residents, non-farmer, obesity and non-vitamin D supplementation were the predictors for vitamin D insufficiency in Thai patients with RA. Conclusion: There are no associations of serum 25(OH)D levels with disease activity or functional status in Thai RA patients. The factors associated with vitamin D insufficiency are Bangkok resident, non-farmer, obesity and not taking vitamin D supplementation.