Impact of treatment with immunomodulators and tumour necrosis factor antagonists on the incidence of infectious events in patients with inflammatory bowel disease

BACKGROUND: Corticosteroids, immunomodulators (IM) and tumour necrosis factor antagonists (anti-TNF) are commonly used in the treatment of inflammatory bowel disease (IBD) but they also supress the defence against infectious disease. The aim of this study was to analyse the incidence of infectious events in patients with IBD and the association to concomitant medical therapy. METHODS: We performed a retrospective medical chart review of patients with IBD aged 18–65 years included in the Swedish Registry of Inflammatory Bowel Disease in the catchment area of Umeå University Hospital, Sweden. Data were collected from the period 01 January 2006, to 31 January 2019. An infectious event was defined as an outpatient prescription of antimicrobials or a positive diagnostic test for infection. RESULTS: During a period of 5,120 observation-years, we observed 1,394 events in 593 patients. The mean number of infectious events per 100 person-years was 27.2 (standard deviation [SD]: 0.46). There were no differences in mean incidence rates between patients treated with no immunosuppression (23.0 events per 100 person-years, SD: 50.4), patients treated with IM monotherapy (27.6 events per 100 person-years, SD: 49.9), patients treated with anti-TNF monotherapy (34.3 events per 100 person-years, SD: 50.1) and patients on combination therapy (22.5 events per 100-person-years, SD: 44.2). In a multivariate logistic regression, female gender (adjusted odds ratio [AOR]: 2.24; 95% confidence interval [CI]: 1.49–3.37) and combination therapy (AOR: 3.46; 95% CI: 1.52–7.85) were associated with higher risks of infection (>32 events per 100 person years). Also, patients treated with any immunosuppression treatment for 25–75% (AOR: 2.29; 95% CI: 1.21–4.34) and for >75% (AOR: 1.93; 95% CI: 1.19–3.12) of the observation period were at higher risks compared to patients treated with immunosuppression <25% of the observation period. CONCLUSION: We observed no significant difference in risk for infections between patients on monotherapy with IM or anti-TNF and patients with low use of immunosuppression, but there was a significant risk for combination therapy.