Stefan Elbers

194 Chapter 7 as a method to integrate stakeholder input into the intervention design, more robust evaluations of co-design–based interventions are required to determine its additional value to existing development practices (Donetto et al., 2015; Robert & Macdonald, 2017). A similar point can be made for the evaluation of mHealth apps. A recent systematic review revealed that health care apps to promote self-management in chronic conditions have seldom been evaluated by randomized controlled trials over a prolonged study period (Byambasuren et al., 2018). This study will help understand if an mHealth app that has been developed by co-design methods not only contributes to an acceptable and user-friendly intervention but also leads to maintenance of treatment gains for patients with chronic pain. Strengths and Limitations Because IMPT progammes often substantially vary in dose and content, the inclusion of multiple treatment centers will positively influence generalization. Furthermore, this study builds on a feasibility study where evaluations related to form, content, and integration within treatment progammes have been incorporated into the current app and study procedures. The exploratory analysis of engagement variables in this study is expected to provide preliminary insight into patient adherence to the behaviour regulation strategies within the app. According to Sieverink and colleagues (Sieverink et al., 2017), insight into adherence to mHealth apps can be acquired by combining usage behaviour data with a description of intended use and a well-substantiated justification for this intended use. Although this may be difficult to quantify as the intended usage of the app depends on fluctuations of patients’ functional status in the posttreatment phase, the comparison of systemusage data with our expectations regarding the use of the strategies will at least provide an indication of adherence to the app. Possible follow-up studies that include qualitative evaluations of patient input may lead to a more sustained insight into adherence. This study includes several challenges and compromises that can potentially bias the outcomes. First, including patients with both treatment conditions within one center increases the risk of contamination. Second, health care providers have a large influence on participant engagement. Our feasibility study indicated that healthcare provider involvement varied greatly between patients, and that patients with limited health care provider feedback did not always use the intervention as intended (Elbers et al., 2020). By scheduling regular contact moments to discuss progress, we aim to minimize the impact of this potential threat. Third, the limited project duration and funding resulted in a maximum follow-up period of 12 months. Although this first year may be crucial for integrating the newly learnedmanagement strategies into a daily life routine, the effect of the AGRIPPA app