The objective of this study was to conduct a fidelity evaluation of a motivational interviewing (MI) intervention delivered by social insurance caseworkers, in a three-arm randomized controlled trial (RCT) for improving return to work for people on sick leave with musculoskeletal disorders. The caseworkers received six days of MI training, including an intervention manual prior to the trial onset, as well as supervision throughout the trial. The caseworkers recorded 21 MI sessions at regular intervals during the trial. An independent MI analysis center scored the recordings using the MI treatment integrity code (MITI 4). In addition, three experienced MI trainers assessed the adherence to the MI intervention manual on a 1-4 Likert scale and MI competence. Total MITI 4 mean scores were at beginning proficiency levels for two components (global technical, mean 3.0; SD 0.6 and the reflections/questions ratio, mean 1.1; SD 0.2) and under beginning proficiency for two components (global relational, mean 3.2; SD 0.7 and complex question, mean 34.0; SD 21.2). The MI trainers' assessment showed similar results. The mean adherence score for the MI sessions was 2.96 (SD 0.9). Despite delivering a thorough course and supervision package, most of the caseworkers did not reach proficiency levels of good MI competence during the study. The fidelity evaluation showed that a large amount of training, supervision and practice is needed for caseworkers to become competent MI providers. When planning to implement MI, it is important that thorough consideration is given regarding the resources and the time needed to train caseworkers to provide MI in a social insurance setting.
Keywords: fidelity; motivational interviewing; musculoskeletal disorder; sick leave.