Stefan Elbers

214 Chapter 8 LIMITATIONS In each chapter, we have already discussed the specific limitations of each study. In this section we will address three main overarching limitations. First, the neglect of relapse in pain research has been the main motivation to start this project. It is therefore important to reflect on what this project has yielded in this area. Although Chapter 2 did not identify overall trends in relapse in longitudinal patient cohorts, the outcome distributions of these measures still leave room for a proportion of individual patients to relapse. We attempted to estimate this proportion but we were not sufficiently confident in these estimates to report them. Consequently, we cannot provide a clear indication of the prevalence of relapse. When more individual patient data become available, it will be possible to better determine the scope of this problem. A second issue is the difficulty of determining what constitutes relapse in the context of IMPT programmes. We circumvented this by focusing on evaluating and supporting the ability to maintain positive treatment gains over time for a broad range of outcome measures. Second, the outcome measures currently used often do not sufficiently reflect meaningful endpoints for patients (Eccleston & Crombez 2019), and vary greatly between studies. A potential solution to allow more accurate measurements is the development of core outcome sets. Although currently under development for patients who participated in IMPT programmes, they are not yet available (Pogatzki-Zahn 2019, Kaiser et al., 2018). The third limitation is that intervention development and feasibility testing were largely performed in two treatment facilities. While increasing mutual understanding and lowering the barriers for activities such as co-design, this also resulted in lower variability in health care professionals involved and in treatment contexts. The outcomes of the AGRIPPA trial should provide more clarity as to what extent this has influenced the outcomes, because that trial also includes additional treatment facilities that offer the intervention. IMPACT By discussing the role of the living systematic review in improving the evidence ecosystem, we have already addressed a part of this project that could have an impact in future rehabilitation science. To facilitate dissemination, we have specifically ensured that our annotated R scripts are open-access for other projects. In addition, there are three other impacts resulting from this project. We will outline these below.