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Background: The positivity thresholds of faecal immunochemical testing (FIT) in colorectal cancer (CRC) screening vary between countries. Aims: To explore the trade‐off between colonoscopies performed, adverse events and lesions detected at different FIT thresholds in a Norwegian CRC screening trial. Methods: We included first participation in biennial FIT screening for 47,265 individuals aged 50–74 years. Individuals with FIT > 15 μg Hb/g faeces were referred for colonoscopy. We estimated the number of colonoscopies, adverse events, screen‐detected CRCs, advanced adenomas and serrated lesions expected at FIT thresholds currently or recently used in other European countries ranging between 20 and 150 μg/g. Results: At the 15 μg/g threshold (Norway), 3705 participants underwent colonoscopy, of whom 203 had CRC, 1119 advanced adenomas and 256 advanced serrated lesions. Using a 47 μg/g threshold, 1826 (49.3%) individuals would have undergone colonoscopy, and 154 (75.9%) would have been diagnosed with CRC, 702 (62.7%) with advanced adenoma and 128 (50.0%) with advanced serrated lesion compared to the 15 μg/g threshold. At 150 μg/g, the corresponding figures would have been 838 (22.6%) undergoing colonoscopy, 114 (56.2%) with CRC, 345 (30.8%) advanced adenoma and 54 (21.1%) advanced serrated lesions. The detection rate of stage I CRC was 0.22% at 15 μg/g and 0.11% at 150 μg/g. Post‐colonoscopy bleeding rates were 0.8% and 1.7%, respectively. Conclusions: Increasing the FIT threshold reduces colonoscopy demand, but substantially decreases lesion detection and unfavourably changes CRC stage distribution. The risk of adverse events at colonoscopy increased with FIT threshold, requiring country‐specific information on adverse events. Trial Registration: Clinicaltrials.gov identifier: NCT01538550 [ABSTRACT FROM AUTHOR]

Aim: To investigate the possible long-term psychological harm of participating in colorectal cancer (CRC) screening in Norway., Methods: In a prospective, randomized trial, 14294 participants (aged 50-74 years) were invited to either flexible sigmoidoscopy (FS) screening, or a faecal immunochemical test (FIT) (1:1). In total, 4422 screening participants (32%) completed the questionnaire, which consisted of the Hospital Anxiety and Depression Scale and the SF-12, a generic health-related quality of life (HRQOL) measurement, when invited to screening and one year after the invitation. A control group of 7650 individuals was invited to complete the questionnaire only, at baseline and one year after, and 1911 (25%) completed the questionnaires., Results: Receiving a positive or negative screening result and participating in the two different screening modalities did not cause clinically relevant mean changes in anxiety, depression or HRQOL after one year. FS screening, but not FIT, was associated with an increased probability of being an anxiety case (score ≥ 8) at the one-year follow-up (5.6% of FS participants transitioned from being not anxious to anxious, while 3.0% experienced the reverse). This increase was moderately significantly different from the changes in the control group (in which the corresponding numbers were 4.8% and 4.5%, respectively), P = 0.06., Conclusion: Most individuals do not experience psychological effects of CRC screening participation after one year, while FS participation is associated with increased anxiety for a smaller group., Competing Interests: Conflict-of-interest statement: All authors declare that they have no conflict of interest.