Colorectal Cancer Screening and Perceived Disgust: The Importance of the “Ick” Factor in Faecal Occult Blood Test Uptake

Background: Colorectal cancer is a major cause of cancer deaths worldwide. Screening is key to early detection but uptake of national programmes is poor, especially amongst those from lower socio-economic backgrounds. Decisions not to take up screening may be based more on emotional rather than rational evaluations. We aimed to examine the importance of perceived disgust (the ‘ICK’ factor) in determining colorectal cancer screening uptake, in a large, randomised controlled trial. Methods: This paper reports secondary analysis of a randomised controlled trial of a simple, questionnaire-based Anticipated Regret (AR) intervention, which was delivered alongside existing pre-notification letters. 60,000 adults aged 5074 who were participant in the Scottish National Screening programme were randomised to one of 3 treatment arms: 1) no questionnaire (control), 2) Health Locus of Control (HLOC) questionnaire or 3) AR questionnaire. Primary outcome was Faecal Occult Blood Test kit return (FOBT uptake). 13,645 people completed questionnaires of secondary outcomes including intention to return test kit and a new self-report measure of perceived disgust (ICK-C). Results: Intentions, ICK and AR were all predictors of FOBT uptake; however, for people who expressed strong intentions to return their FOBT kit, only ICK differentiated kit returners from non-returners, with non-returners reporting higher disgust (mean difference=0.51; 95% CI for difference (0.37, 0.64), Cohen’s d=0.34). The 4-item ICK-C showed excellent internal reliability and predictive validity with regard to an objective measure i.e., FOBT uptake. Conclusions: The findings show that perceived disgust is an important emotional psychological construct in determining uptake of colorectal cancer screening. We also demonstrated that a simple 4-item scale (the ‘ICK-C), developed to be used in research on colorectal cancer screening, has excellent psychometric properties.