P012 THE EFFECT OF VITAMIN D DEFICIENCY, AND ITS CORRECTION, ON CLINICAL OUTCOMES IN INFLAMMATORY BOWEL DISEASE (IBD)

Abstract

Vitamin D (25OH) deficiency is highly prevalent in patients with inflammatory bowel disease (IBD). Observational studies have associated this with increased disease activity, but small vitamin D supplementation studies have not improved clinical outcomes. Here, we undertake a case-control study to compare healthcare utilization in patients with sustained vitamin D deficiency to those whose 25OH levels have been corrected. An electronic medical record (EMR) search query was used to identify all patients at a single medical center with a diagnosis code for IBD and two recorded 25OH levels (at T0 and T1) within an 18-month time window. The EMR of this cohort was searched for all clinic, emergency, and hospital visits in the 24 months after T0. Patients were grouped by 25OH levels to three groups; ‘low’ (<20ng/mL), ‘high’ (>30ng/mL), and ‘restored’ (T0 <20ng/mL, T1 >30ng/mL). Proportions were compared between groups using χ2 test or Fisher’s exact test for dichotomous data, and t-test or Mann-Whitney test for comparison of means. Logistic regression modelling was utilized to obtain propensity scores and match controls (‘low’) to cases (‘restored’) to estimate a treatment effect of correction of vitamin D levels to >30ng/mL, when controlled for confounding variables. Data on 410 patients were analyzed; mean age 58 years, 68% female, and 81% white. Ulcerative colitis (UC) and Crohn’s disease (CD) were equally distributed (51% and 49%). The ‘low’ cohort consisted of 36 patients (mean 25OH 14ng/mL), the ‘high’ cohort had 129 patients (mean 25OH 48ng/mL) and the ‘restored’ included 69 patients (mean 25OH 41ng/mL after correction). Mean number of IBD-related clinic visits was 4, and 14% had more than one IBD-related ED visit or hospitalizations over 24 months. For the entire cohort, and for those with CD, ‘low’ vitamin D status was not associated with an increased risk of IBD-related clinic, emergency, or hospital visits, when compared to ‘high’ vitamin D status patients. Only in patients with UC was there a difference in the proportion of IBD-related hospitalizations between ‘low’ and ‘high’ groups (22% v. 6%, p=0.02). Patients who converted from ‘low’ to ‘high’ vitamin D status (‘restored’) increased their mean 25OH from 15ng/mL to 41ng/mL. There was no statistical difference in any outcome between matched controls (‘low’) and cases (‘restored’) over 24 months follow-up. Power for these analyses was confirmed to be >0.8 for dichotomous outcomes based on this sample size and proportions. Persistently ‘high’ (>30ng/mL) vitamin D levels, or restoration of levels from <20ng/mL to >30ng/mL, did not reduce IBD-related healthcare utilization over 24 months in this observational study of 410 patients. There may be a benefit in retaining levels >30ng/mL in patients with ulcerative colitis.