Prevalence and Risk Factors for Functional Vitamin B12 Deficiency in Patients with Crohn's Disease

Background:Crohn's disease (CD) is a risk factor for vitamin B-12 deficiency due to frequent involvement of the terminal ileum. Conventional screening for B-12 deficiency with serum B-12 is relatively insensitive and measures total B-12 concentration, of which a minority is present in a biologically active form. Holotranscobalamin (holoTC) combined with methylmalonic acid (MMA) is believed to be more accurate in identifying impaired B-12 status. We evaluated the prevalence and risk factors for B-12 deficiency using holoTC supported by MMA among patients with CD.Methods:We performed a single-center service evaluation of 381 patients with CD who underwent B-12 assessment (holoTC/MMA) and compared them with 141 patients with ulcerative colitis. Eighty-nine patients with CD underwent paired serum B-12 and holoTC. Among patients with CD, risk factors including terminal ileal resection length, ileal inflammation on endoscopy, and disease characteristics on magnetic resonance imaging were recorded.Results:Prevalence of B-12 deficiency among patients with CD was 33% compared with 16% in ulcerative colitis (P < 0.0001). In 89 patients who underwent paired tests, conventional testing identified B-12 deficiency in 5% of patients with CD, which increased to 32% using holoTC/MMA. Independent risk factors for B-12 deficiency were ileal resection length 20 cm (odds ratio: 3.0, 95% confidence interval, 1.5-6.0, P = 0.002) and >20 cm (odds ratio: 6.7, 95% confidence interval, 3.0-14.7, P < 0.0001) and ileal inflammation (odds ratio: 3.9, 95% confidence interval, 2.2-6.9, P < 0.0001). On magnetic resonance imaging, active terminal ileal inflammation (P = 0.02) and an increased disease burden (1 skip lesion, P = 0.01 and prestenotic dilatation >3 cm, P = 0.01) were associated with B-12 deficiency.Conclusions:Vitamin B-12 deficiency is common in patients with CD. holoTC supported by MMA identifies patients with B-12 deficiency considered replete on conventional testing.