Protocol for an open-label feasibility study for a randomised controlled trial of vitamin D supplementation in...

Crohn's disease (CD) is a principal form of inflammatory bowel disease, affecting approximately 1 in every 650 people in the UK. Vitamin D deficiency is common in approximately 57.7% of CD patients; with anaemia occurring in about 43% of patients. There is growing evidence that supplementing CD patients who are vitamin D deficient may be effective in reducing the severity of CD symptoms and reducing iron-deficiency anaemia. Nevertheless, National Institute for Health and Care Excellence guidance regarding the management of CD does not address vitamin D deficiency in these patients. The aims of the study are (1) to determine the prevalence of vitamin D deficiency in adults with CD in Birmingham, UK and (2) to assess the feasibility of conducting a multi-site randomised controlled trial in adult patients with CD and vitamin D deficiency.

D-CODE consists of two parts-a screening study and an open-label randomised controlled feasibility study. 1. Vitamin D screening Three hundred patients, 18 years or older with CD will have a dried blood spot test to measure vitamin D levels. Dietary and sun exposure data will be collected. Eligible patients with low levels of vitamin D will be invited to participate in the feasibility study. 2. Feasibility study Fifty participants with CD and vitamin D deficiency will be randomised to receive either a low (400 IU daily for 24 weeks) or high (3200 IU daily for 12 weeks then vitamin D3 800 IU daily for 12 weeks) dose of vitamin D3 oral supplementation. Patient-reported outcomes (Inflammatory Bowel Disease Questionnaire, EQ-5D-5L and Crohn's Disease Activity Index Score) will be collected at weeks 0 and 24. Biochemical monitoring will take place at weeks 0, 12 and 24 and will measure 25-hydroxyvitamin D, corrected calcium, albumin, parathyroid hormone, hepcidin, other vitamin D metabolites, iron studies and C-reactive protein. Faecal calprotectin will be measured at weeks 0 and 24.

A key aspect of D-CODE is the identification of vitamin D deficiency prior to supplementation. It is hoped that this feasibility study will lead to a definitive trial that will investigate the benefits of treating vitamin D deficiency in patients with CD.

The trial has been registered with EudraCT number 2018-003910-42, ClinicalTrials.gov identifier NCT03718182 and ISRCTN number 15717783.