Conceptual framework

Intervention and trial design are guided by the Health Belief Model (HBM),²⁴ the Precaution Adoption Process Model and Self-Determination Theory.^25–28 The HBM suggests that people’s use of preventive services is explained by their perceived threat of disease, benefits of the service, barriers to and self-efficacy for obtaining screening. The model also acknowledges the need for a stimulus, or cue to action, to trigger the behaviour. The HBM provides overarching guidance for intervention design (eg, provision of information regarding the risks and consequences of CRC, and the benefits of screening; offering assistance overcoming barriers to screening; and addressing structural barriers to completing screening by providing direct access to stool testing and assistance with completing screening) as well as the impetus for targeting patients immediately following a primary care visit with an order for CRC screening (ie, an external cue to action that has occurred within established clinic processes). The HBM, however, does not provide guidance on how to personalise health communications and other intervention components to maximise message salience and accompanying action. The Precaution Adoption Process Model provides this guidance by building on the core elements of the HBM and considering how a person comes to decisions to take action.²⁶ Specifically, the individual’s readiness to engage in the healthful behaviour is based on their ‘decision stage’. The premise behind the model is that different factors influence different stage transitions and that messages can be strategically designed to move individuals through the stages.^{29 30} For example, the e-assist: Colon Health programme offers patients who indicate they are not ready to be screened suggestions for how to overcome common personal barriers to screening. Likewise, patients who indicate they are undecided about how to be screened are provided with information about the pros and cons of different test options, while those indicating they are ready to be screened are provided with tips for completing their preferred screening test and assistance removing structural barriers that may arise. Finally, we use principles from Self-Determination Theory to guide the tone of the written messages and ensure they are autonomy supporting²⁸ and are not overly directive or controlling. For example, the programme provides information on other types of CRC screening tests only to those who express an interest in this information and then emphasises that modality choice is up to the patient.