Vitamin D Deficiency Increases the Risk for Moderate to Severe Disease Activity in Crohn's Disease Patients in South Africa, Measured by the Harvey Bradshaw Index

Objective: Vitamin D has immunoregulatory properties and appears to influence disease outcomes in patients with Crohn's disease (CD). The primary aim of this study was to evaluate the association between vitamin D status and CD activity in South Africa.Methods: In a cross-sectional study performed between September 2011 and January 2013, serum 25-hydroxyvitamin D (25(OH)D) was measured in 186 consecutive patients with CD seen at 2 inflammatory bowel disease (IBD) centers and 199 healthy controls in the Western Cape, South Africa. Lifestyle and clinical variables were identified using an investigator-administered questionnaire, as well as clinical examination and patient case notes. Vitamin D status was evaluated in 2 ways: 20ng/mL vs 21ng/mL and 29ng/mL vs 30ng/mL. Disease activity was measured by the Harvey Bradshaw Index (HBI). Various 25(OH)D threshold concentrations for predicting a higher HBI score were also investigated.Results: On multiple log-binomial regression analysis, higher HBI scores and not having taken vitamin D supplementation in the 6months prior to enrollment were identified as risk factors for vitamin D deficiency in patients with CD, defined either as 20ng/mL or as 29ng/mL (p < 0.03). Compared to patients with HBI < 5, those with HBI 8 were 2.5times more likely to have 25(OH)D concentrations 21ng/mL (prevalence risk [PR] = 2.5; 95% confidence interval [CI], 1.21-6.30). The risk was similar, though not as high, when defined as 29ng/mL (PR = 2.0; 95% CI, 1.13-3.51). When vitamin D deficiency was defined as <20, <30, <40, and <50ng/mL, the sensitivity and specificity obtained were 44.9% and 78.8%; 75.5% and 62.4%; 86.7% and 44.7%; and 92.9% and 23.5%, respectively (area under the curve = 0.71; p < 0.0001).Conclusion: Low serum 25(OH)D was associated with increased CD activity in a South African cohort.