Does theory of planned behaviour play a role in predicting uptake of colorectal cancer screening? A cross-sectional study in Hong Kong

OBJECTIVE: Colorectal cancer (CRC) ranked second in terms of cancer mortality worldwide. It is associated with a substantial global disease burden. We aimed to examine whether the theory of planned behaviour (TPB) could predict the uptake of faecal immunochemical test to inform novel strategies for enhancing CRC screening participation in population-based programmes. DESIGN: Cross-sectional study. SETTINGS: A Hong Kong-based and territory-wide telephone survey was conducted during the study period from October 2017 to November 2018. PARTICIPANTS: 4800 asymptomatic individuals aged 61-70 years who can communicate in Cantonese were recruited during the survey period. Those who had a history of CRC, chronic bowel inflammation, two or more first-degree relatives with CRC, and received colonoscopy in the past 10 years or faecal occult blood test in the past 5 years were excluded. OUTCOME MEASURES: The association between CRC screening uptake and the factors pertinent to TPB was analysed by univariable and multivariable regression models and the mediating effect of intention. We adjusted for age, gender, educational level, marital and working status, as well as household income. RESULTS: Multivariable regression analysis showed that high perceived behavioural control (adjusted OR (AOR)=12.35, 95% CI 8.21 to 18.60, p<0.001), high intention for CRC screening (AOR=7.86, 95% CI 6.60 to 9.36, p<0.001) and positive attitude towards CRC screening (accuracy and effectiveness: AOR=1.19, 95% CI 1.03 to 1.38, p<0.05; embarrassment and apprehension: AOR=4.27, 95% CI 3.13 to 5.82, p<0.001) were significantly associated with CRC screening uptake. Mediation analysis found that the effect of social norms on screening behaviour was primarily mediated by intention (83.2%), and this indirect, mediated effect accounted for 21.7% to 24.1% of total effects of other constructs in TPB on screening behaviour. CONCLUSIONS: The variables pertinent to TPB could successfully predict CRC screening uptake. Promotion of CRC screening based on interventions that increase perceived behavioural control and behavioural intention could potentially enhance screening uptake. Further studies are needed to establish the cause and effect relationship among these variables and screening uptake, as well as to evaluate the cost-effectiveness of such interventions.