Process evaluations aim to explore which components of the intervention are more important in achieving the outcome (9). Our study has identified several components considered pivotal in this achievement. However, the mechanisms are often the result of synergistic effects between components in a particular context, and this needs to be considered when understanding the findings (14, 30). The most important contextual mechanisms were those created by the TC which interacted with most components in the programme. Our findings showed that continuity, confidentiality and being able to talk about sensitive issues in a safe space were pivotal for the adolescents. These needs have been expressed in preparatory studies (31–33) and are considered an essential part of adolescent health (22, 23, 34). Moreover, as empowerment can be seen as both a process and an outcome (13) the creation of an equal caring relationship that builds on PCC is an example of an empowering process where shared-decision making was one of the outcomes. Furthermore, health-related learning was a recurring theme in the results. Goal setting was most often related to learning about one’s CHD and how to communicate this to others. This finding might be especially common to adolescents with CHD, where disease-related knowledge is low (31, 35, 36). However, the educational process and the provision of tailored learning strategies were a central aspect of this achievement. Indeed, active learning was one behaviour-change technique selected in the intervention development phase (18), indicating that this component was delivered successfully. Another important finding was the meaning of peer support. This component was experienced by many as most impactful. Transition interventions in other patient populations have shown similar results (37), highlighting the importance of meeting others with similar conditions. However, our results showed that there were some limitations in the delivery of this component. For instance, several participants did not attend the information day due to feeling uncomfortable about interacting with other adolescents with CHD. Previous studies have shown that adolescents lack of engagement in their illness affects study participation negatively (15). In addition, group dynamic and not being able to identify with the role models during the information day were seen as shortcomings. Indeed, for role models to be effective the participant has to be able to identify with them (38, 39). As the CHD population is diverse in regard to disease complexity and longevity throughout the life course (40), role models used in future transition interventions should consider this diversity.
Our findings showed that although most components were experienced positively and achieved increased empowerment, some were delivered insufficiently or did not receive the desired response. Parents did not consider themselves involved in the programme, which for some resulted in ambivalence about changing roles. As parents are an important resource in the adolescents’ transition to adulthood (41, 42) this was a shortcoming in the implementation of the programme. However, not all parents expressed the need for additional guidance. Tailoring to the family’s needs is therefore important for future studies. Another component that was poorly implemented according to the findings was the transfer meeting with adult care. A reason for the experienced asynchrony between the intervention and usual care might be that follow-up visits are defined according to CHD complexity, ranging from one to every three to five years (26). Thus, the follow-up visit in usual care did not always synchronize with the transfer meeting in the intervention. Our findings therefore emphasize the need for a more person-centred approach towards transfer and transition, whereby follow-up visits are based on the patients’ health needs in addition to medical parameters.
Some methodological limitations must be addressed. Thirteen out of 27 adolescents and 8 out of 20 parents declined participation or were unreachable. The transferability of findings in relation to possible selection bias must therefore be considered, as the sample may have had more positive experiences of the intervention. The sample was nevertheless representative of the whole group of participants in the transition programme (Table 1). The use of various forms of interviews gave participants the opportunity to select their preferred medium of communication (27, 28) meaning a wide range of perspectives on the intervention were gathered. Recall bias may be considered another limitation, as the intervention period was 2.5 years and the interviews were performed after participation. However, the timing of interviews was appropriate, as performing them earlier may have affected the effectiveness evaluation due to this study being based on experiences and mechanisms leading to outcomes. We used method triangulation to deal with recall bias in our process evaluation (9, 43). By using participatory observations, interviews and quantitative assessments of the components and implementation steps we aim to capture different aspects of the intervention in future studies (11).
In light of these limitations, our study has several strengths. Firstly, the use of intervention mapping (a proven intervention development framework) (44) facilitated the successful delivery of an intervention that reached the performance objectives stated in the logic model (18). Moreover, the outcomes presented in this study respond to findings from the preparatory studies, which ensures credibility and transferability of our results (45). Secondly, the findings of this study were analysed and reported before knowing the outcome of the effectiveness evaluation, thus avoiding biased interpretation of future findings (9). As a result, this study generates a hypothesis on how the intervention worked and can shed light on mechanisms responsible for working towards the outcome, as well as components that were implemented poorly and can hamper outcomes. Thirdly, as parents have a central role in the transition (46, 47), including them in this study has identified moderating factors on the mechanisms of the transition programme and highlighted components that were insufficiently delivered. Moreover, using different interviewers for adolescent and parent interviews (i.e., investigator triangulation) allowed us to handle bias associated with using one principal interviewer (43), thus increasing dependability and credibility of findings (45). Finally, by sampling participants with varied adherence to the components of the programme, we gained perspectives on how the programme and its components were perceived. These findings are especially important for the implementation of transition programmes in other settings and populations.