Vitamin D Status in Egyptian Patients with Rheumatoid Arthritis

Background: Vitamin D is a potent regulator of calcium homeostasis and may have immunomodulatory effects. The influence of vitamin D on human autoimmune disease has not been well defined. The aim of this cross sectional study was to estimate the prevalence and determinants of vitamin D deficiency in patients with rheumatoid arthritis as compared to healthy controls and to analyze the association between 25-hydroxyvitamin D with disease activity. Methods: The study includes 55 consecutive rheumatoid arthritis patients and 25 healthy controls, not on vitamin D supplements. Together with parameters of disease activity, all patients had serum 25-hydroxyvitamin D [25(OH) D] measured by ELISA kit in a centralized laboratory. Disease activity in rheumatoid arthritis was assessed by Disease Activity Score 28 (DAS28) and Health Assessment Questionnaire (HAQ). According to activity indexes, patients were divided into subgroups with high activity of the disease (DAS28 > 5.1), moderate activity of the disease (3.2 < DAS28 <= 5.1), low activity of disease (2.6 <= DAS28 <= 3.2) and remission (DAS28 < 2.60). Associations between serum levels of 25(OH) D and age, disease duration and activity were assessed. Results: 25-hydroxyvitamin D deficiency, insufficiency and sufficiency were found in 16.00, 4.00 and 80.00 % of controls, respectively, while, 25(OH) D insufficiency and sufficiency were found in 21.80 and 78.20 % of rheumatoid arthritis patients, respectively with no significant difference between groups (P < 0.918). According to DAS28 scoring, 9.10 % of patients showed remission (DAS28 < 2.6), 7.30 % showed low disease activity (2.6 <= DAS28 <= 3.2), 63.60 % showed moderate activity (3.2 < DAS28 <= 5.1) and 20.00 % showed high disease activity (DAS28 > 5.1). Disease duration was significantly longer in patients with moderate disease activity vs. those with low and high disease activity (P < 0.026 and P < 0.001, respectively). 25(OH) D levels were lower in moderate disease activity vs. those with remission (P < 0.014). DAS28 and HAQ were significantly higher in patients with high disease activity than remission, low disease activity and moderate disease activity. DAS28 and HAQ were significantly higher in patients with moderate disease activity than remission and those with low disease activity. A significant negative correlation was found in rheumatoid arthritis patients between 25(OH) D and ESR. Conclusions: In rheumatoid arthritis patients, vitamin D deficiency is quite common, but similar to that found in control subjects; disease activity (expressed as ESR) is inversely related to 25(OH) D levels.