Undiagnosed inflammatory bowel disease among individuals undergoing colorectal cancer screening: a nationwide Danish cohort study 2014–2018

Correspondence to Dr Tine Jess, Center for Molecular Prediction of Inflammatory Bowel Disease, PREDICT, Department of Clinical Medicine, Aalborg Universitet, Copenhagen, Denmark; jess@dcm.aau.dk Chiu et al recently investigated the long-term effectiveness of national faecal immunochemical test (FIT) screening for colorectal cancer (CRC).1 They demonstrated reduced risk of advanced-stage CRC and its mortality with larger reductions in distal CRC as compared with proximal CRC. The prevalence of IBD is up to 1% in westernised countries.2 3 However, symptoms of IBD vary and may increase time to diagnosis.4 Correct and early diagnosis is important to improve treatment outcomes and patients’ quality of life.5 Although early markers of IBD, such as antimicrobial antibodies and serum proteins, are emerging,6 7 colonoscopy still remains one of the only methods to detect early IBD. Since 2014, colonoscopy has been offered to all Danes aged 50–74 years with a positive FIT test in the nationwide Danish screening programme for CRC.8 The suggested prevalence of undiagnosed IBD ranges from 1.8%9 to 3.8%,10 but remains unknown in high-risk countries as the Scandinavian. [...]the prevalence of undiagnosed IBD was 0.04% in the general Danish population aged 50–74 years (figure 1).