1Division of Gastroenterology, University of Alberta, Edmonton, Alberta, Canada.
Vitamin D is a key immunomodulator and its deficiency is prevalent among Crohn's patients. The interaction between vitamin D and the response to infliximab induction therapy has not been previously described.
Patients with moderate-severe Crohn's disease, defined as having a modified Harvey Bradshaw index ≥8, who were being induced with infliximab were recruited. Patients were divided into low and normal vitamin D groups. Patients were followed prospectively for 14 weeks for achievement of clinical remission (Harvey Bradshaw index <5). At week 14, vitamin D deficient patients were supplemented with intramuscular cholecalciferol; all patients were re-assessed at week 22. Serum cytokine levels were measured at weeks 0, 14, and 22.
Twenty-eight patients initiating infliximab were included, with 54% of patients in the low vitamin D group. The proportion of patients in clinical remission was greater in the low vitamin D group compared with the normal vitamin D group at both week 14 (80% versus 23%, P = 0.007) and week 22 (79% versus 17%, P = 0.005). The low vitamin D group had higher baseline IL-6 levels (median, 4.4 [interquartile range, 2.0-5.7] versus 1.1 [0.8-1.7] pg/mL, P = 0.004) and lower interleukin-12 levels (0.3 [0.1-0.4] versus 0.5 [0.5-0.6] pg/mL, P = 0.006) compared with the normal vitamin D group. At week 14, IL-8 levels were significantly lower in the low vitamin D group compared with the normal vitamin D group (11.2 [9.1-13.8] versus 20.5 [17.9-37.2] pg/mL, P = 0.005).
Crohn's patients initiating infliximab with a low vitamin D level are more likely to achieve infliximab-induced clinical remission at week 14.