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: ≤20 ng/mL vs ≥21 ng/mL and ≤29 ng/mL vs ≥30 ng/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 6 months prior to enrollment were identified as risk factors for vitamin D deficiency in patients with CD, defined either as ≤20 ng/mL or as ≤29 ng/mL (p < 0.03). Compared to patients with HBI < 5, those with HBI ≥ 8 were 2.5 times more likely to have 25(OH)D concentrations ≤21 ng/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 ≤29 ng/mL (PR = 2.0; 95% CI, 1.13–3.51). When vitamin D deficiency was defined as <20, <30, <40, and <50 ng/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.