Fidelity of delivery and contextual factors influencing children’s level of engagement with an online behavioural intervention for tics: Process evaluation of the ORBIT trial (Preprint)

BACKGROUND The Online Remote Behavioural Intervention for Tics (ORBIT) study was a multicentre randomized controlled trial of a complex intervention that consisted of an online behavioural intervention for children and young people (CYP) with tic disorders. In this first part of a two-stage process evaluation, we conducted a mixed-methods study exploring reach, dose, and fidelity of the intervention and contextual factors influencing engagement with the intervention. OBJECTIVE This study aims to explore the fidelity of delivery and the contextual factors underpinning the ORBIT intervention. METHODS Baseline study data and intervention usage metrics from participants in the intervention arm were used as quantitative implementation data (n=112). The experiences of being in the intervention were explored by semi-structured interviews with children (n=20) and parent (n=20) participants, therapists (n=4), and referring clinicians (n=6). A principal components analysis was used to create a comprehensive, composite measure of CYP’s engagement with the intervention. Engagement factor scores reflected relative uptake as assessed by a range of usage indices including chapters accessed, number of pages visited and number of logins. RESULTS The intervention was implemented with high fidelity, and participants deemed the intervention acceptable and satisfactory. Engagement and adherence were high with child participants completing an average of 7.5/10 chapters and 100/112 (89.3%) participants completed a minimum of 4 chapters: the pre-defined threshold for effective dose. Compared to the total population of children with tic disorders, the sample tended to have more educated parents and live in more economically advantaged areas but socioeconomic factors were not related to engagement factor scores. Factors associated with higher engagement factor scores included participants enrolled at the London site vs. the Nottingham site (P=.011), self-referred vs. clinic-referred (P=.041), higher parental engagement as evidenced by number of parental chapters completed (ρ=0.73, n=111, P<.001) and more therapist time for parent (ρ=0.46, n=111, P<.001). A multiple linear regression indicated that parents’ chapter completion (β=.69, t110=10.18, P<.001) and therapist time for parent (β=.19, t110=2.95, P=.004) were the only significant independent predictors of engagement factor scores. CONCLUSIONS Overall, the intervention had high fidelity of delivery and was evaluated positively by participants, although reach may have been constrained by the nature of the randomized controlled trial. Parental engagement and therapist time for parent were strong predictors of intervention implementation which has important implications for the design and implementation of digital therapeutic interventions into Child and Adolescent Mental Health Services. CLINICALTRIAL International Standard Randomized Controlled Trial Number (ISRCTN) 70758207; https://doi.org/10.1186/ISRCTN70758207 and ClinicalTrials.gov NCT03483493; https://clinicaltrials.gov/ct2/show/NCT03483493 INTERNATIONAL REGISTERED REPORT RR2-https://doi.org/10.1186/s13063-019-3974-3