Supplementary Material for: High Serum Creatine Kinase Levels in Infliximab and Vedolizumab-Treated Inflammatory Bowel Disease Patients

Background: TNF inhibitors are relatively safe drugs, but asymptomatic infliximab-induced high serum creatine kinase (CK) levels have been reported in >30% of patients with inflammatory bowel disease (IBD). Whether high serum CK levels are a specific effect of treatment with TNF inhibitors has not been studied in detail. CK levels were therefore compared between infliximab- and vedolizumab-treated IBD patients. Methods: In this retrospective, monocentric study, 131 IBD cases (82 with Crohn’s disease (CD), 49 with ulcerative colitis) of the Basel University Hospital IBD cohort treated either with infliximab or vedolizumab were included. Serum samples for measuring CK, lactate dehydrogenase (LDH), C-reactive protein (CRP), and fecal calprotectin (FCal) levels were collected longitudinally and analyzed using mixed additive models. Results: No significant differences in CK levels between infliximab and vedolizumab-treated patients were observed over time. Infliximab-treated males, however, showed significantly higher CK levels than females and former smokers treated with infliximab showed significantly lower CK levels than nonsmokers. No such differences were observed in vedolizumab-treated patients. LDH and CRP were not significantly different between infliximab- and vedolizumab-treated patients, while adjusted groups showed substantially higher LDH levels with increasing age and significantly lower LDH levels in patients with longer disease duration. Infliximab patients with CD showed significantly lower CRP. However, significantly higher FCal concentrations were noted in infliximab patients independent of diagnosis, gender, disease duration, smoking behavior, and age. Conclusion: In our cohort, high serum CK levels are not an infliximab- or vedolizumab-specific effect.