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

Abstract

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.

Key words:

• vitamin D
• Crohn's disease
• 25(OH)D
• inflammatory bowel disease
• Harvey Bradshaw Index
• deficiency
• South Africa

ACKNOWLEDGMENTS

The authors thank Mr. and Mrs. Raffner, Dr. Ernesta Kunneke, Karin Fenton, and Amanda Fourie for their inspiring and administrative assistance of this research.

CONFLICT OF INTEREST

The authors declare that there are no conflicting/competing interests (financial, personal, professional, or otherwise) with AstraZeneca/SAGES, the commercial funding source of this research, and/or relating to ownership of stocks or shares, paid employment or consultancy, board membership, research grants (from any source, restricted or unrestricted), travel grants and honoraria for speaking or participation at meetings, gifts of any kind, or patent applications (pending or actual), including individual applications or those belonging to the institution to which authors are affiliated and from which the authors may benefit.

FUNDING

This research was supported by the 2011 Scholarship in Gastroenterology, a scholarship from the AstraZeneca/South African Gastroenterology Society (SAGES). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the article. http://www.sages.co.za/D_AN_ScholTravel.asp