title: 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).
  
  
  CONCLUSIONS
  Low serum 25(OH)D was associated with increased CD activity in a South African cohort.
authors.affiliation: a Dietetics Department.
authors.forename: Abigail
authors.initials: A
authors.lastname: Raffner Basson
authors.forename: Rina
authors.initials: R
authors.lastname: Swart
authors.affiliation: b Statistics and Population Studies Department.|c University of the Western Cape, Bellville, Western Cape, SOUTH AFRICA; Biostatistics Unit, Medical Research Council of South Africa , Parow , Western Cape , SOUTH AFRICA.
authors.forename: Esme
authors.initials: E
authors.lastname: Jordaan
authors.affiliation: c University of the Western Cape, Bellville, Western Cape, SOUTH AFRICA; Biostatistics Unit, Medical Research Council of South Africa , Parow , Western Cape , SOUTH AFRICA.
authors.forename: Mikatako
authors.initials: M
authors.lastname: Mazinu
authors.affiliation: d Department of Gastroenterology , Groote Schuur Hospital , Cape Town , Western Cape , SOUTH AFRICA.|e Department of Medicine , University of Cape Town , Cape Town , Western Cape , SOUTH AFRICA.
authors.forename: Gillian
authors.initials: G
authors.lastname: Watermeyer
mesh_terms: D000328:Adult; D003424:Crohn Disease / Q000150:complications* / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D014808:Vitamin D Deficiency / Q000150:complications* / Q000453:epidemiology*
keywords: 25(OH)D; Crohn's disease; Harvey Bradshaw Index; South Africa; deficiency; inflammatory bowel disease; vitamin D