Is vitamin D a useful biomarker in inflammatory bowel diseases?

Abstract

Background and Aim: Vitamin D has been shown to play a role in inflammation in multiple conditions, including inflammatory bowel disease (IBD). Low vitamin D levels have been shown to be associated with active IBD in retrospective studies. Some evidence of an inverse correlation with disease activity and inflammatory markers exists. The current gold-standard inflammatory marker is fecal calprotectin (FC); however, FC testing is not reimbursed in Australia, and sample collection is not as simple as blood testing. We aimed to assess whether serum vitamin D level is useful as a biomarker in real time. Method(s): Quality assurance ethical approval was obtained from the hospital ethics committee. We collected retrospective data via a chart review of the hospital pathology system and medical records. Patients were initially identified using the pathology database to find those who had FC measured in 2019; then, a subset of patients with IBD with both FC and blood tests within 3 months was selected. Demographic data, IBD type, inflammatory markers, and vitamin D levels were obtained from patient records. The vitamin D levels were compared with levels of FC (with a positive FC level being set at 150 mug/g), C-reactive protein (CRP), albumin, hemoglobin, and platelets. Non-parametric tests were used for comparison. Result(s): We identified 616 patients from the initial cohort with FC tests. There were 328 patient episodes with matched FC and blood tests, including vitamin D, CRP, albumin, hemoglobin, and platelets. This subset comprised 101 patients with Crohn's disease (CD) with 198 time points of matched data and 68 patients with ulcerative colitis (UC) with 116 time points of matched data. There were 14 IBD-unspecified episodes. Of the patients with CD, 46% were male, and of the patients with UC, 43% were male. Median disease duration was 8 years (interquartile range, 4-13.5 years) for those with CD and 5.5 years (interquartile range, 3-12.5 years) for those with UC. Overall, there was a negative correlation between FC and vitamin D levels (Spearman correlation r = -0.19, P < 0.001). This was evident in both the CD and UC subsets (Table 1). Spearman correlations were also carried out for the other serum parameters compared with vitamin D. These were significant in patients with CD for platelet levels only and in patients with UC for CRP, albumin, platelet, and hemoglobin levels (Table 1). Conclusion(s): Lower vitamin D levels appear to correlate with other disease activity biomarkers in patients with IBD, particularly in those with UC. Decreased vitamin D levels may signal a subclinical worsening of inflammation in IBD and suggest that further objective assessment of disease activity is required. Prospective evaluation of vitamin D levels over time is required to ascertain when changes in vitamin D occur.