Profiles of vitamin D among patients with rheumatoid arthritis at the Kenyatta National Hospital

Abstract

Background: Rheumatoid Arthritis (RA) is an autoimmune, chronic debilitating condition of undetermined cause. It affects numerous extra-articular organ systems. Vitamin D is a steroid hormone synthesized in the skin by the action of ultraviolet B (UVB) irradiation. Active vitamin D is important in the inhibition of T cell proliferation and down-regulation of key inflammatory cytokines responsible for the pathogenesis of RA. There is growing evidence demonstrating the association between vitamin D insufficiency and higher incidence of RA as well as increased severity of disease and increased functional disability in RA patients.

Objective: The purpose of this study was to determine serum vitamin D levels among patients with rheumatoid arthritis at the Kenyatta National Hospital (KNH) and its association with disease activity and functional disability.

Design: This was a descriptive cross-sectional survey.

Methods: The study involved subjects with RA at the Kenyatta National Hospital. Consecutive sampling technique to recruit patients with rheumatoid arthritis, having met the 2010 American College of Rheumatology/ European League Against Rheumatism (ACR/EULAR) classification criteria was selected. Ten mls of peripheral blood was collected from the recruited subjects to determine serum vitamin D levels. Every participant had their demographics, clinical history and disease duration documented. Clinical Disease Activity Index (CDAI) was used to assess disease activity and severity. It comprised of number of tender joint out of 28 joints (T-28), number of swollen joints out of 28 (S-28) global health assessment score by both the physician and the patient. Level of disability was determined by the standard Modified Health Assessment Questionnaire (MHAQ). Data analyzed was correlated to determine their association with serum vitamin D levels. SPSS version 21 was used to analyze the data collected and this entailed descriptive statistics, chi-square, ANOVA and students’-test to compare and correlate vitamin D levels with age, duration of disease, CDAI score and modified HAQ score in RA.

Results: Eighty one patients with a mean age of 48.7 (SD 13.9), median of 48.0 (IQR 40.0-59.0) were evaluated. The female to male ratio was 4:1. The mean serum 25-VD concentration was 34.9ng/ml (SD11.6). Thirty five participants (43.2%) had insufficient vitamin D levels (<30ng/ml), whereas 46 study participants (56.8%) had sufficiency of vitamin D. Majority of the patients 54 (67.5%) had low disease activity. Fourteen subjects 17.5% had high disease activity and while 2.5% were on remission. Functional disability was assessed using the modified health assessment questionnaire. Thirty eight participants (46.5%) demonstrated no disability, 33.8% had mild disability while 9% had severe disability. Correlation between vitamin levels with age, duration of disease, CDAI and HAQ did not attain statistical significance.

Conclusion: Vitamin D insufficiency is high among patients with rheumatoid arthritis with no correlation with age, duration of disease, functional disability and disease activity.