LAUSR

Abstract Background Serious infections have been observed in patients with inflammatory bowel disease (IBD) on anti-TNF use—but to what extent these infections are due to anti-TNF or the disease activity per se is hard to disentangle. We aimed to describe how the rates of serious infections change over time both before and after starting anti-TNF in IBD. Methods Inflammatory bowel disease patients naïve to anti-TNF treatment were identified at 5 centers participating in the Swedish IBD Quality Register, and their medical records examined in detail. Serious infections, defined as infections requiring in-patient care, the year before and after the start of anti-TNF treatment were evaluated. Results Among 980 patients who started their first anti-TNF therapy between 1999 and 2016, the incidence rate of serious infections was 2.19 (95% CI,1.43-3.36) per 100 person years the year before and 2.11 (95% CI, 1.33-3.34) per 100 person years 1 year after treatment start. This corresponded to an incidence rate ratio 1 year after anti-TNF treatment of 0.97 (95% CI, 0.51-1.84). Compared with before anti-TNF therapy, the incidence of serious infection was significantly decreased more than 1 year after treatment (incidence rate ratio 0.56; 95% CI, 0.33-0.95; P = .03). Conclusions In routine clinical practice in Sweden, the incidence rate of serious infection among IBD patients did not increase with anti-TNF therapy. Instead, serious infections seemed to decrease more than 1 year after initiation of anti-TNF treatment.