Background
Fidelity refers to the degree to which the delivery of an intervention adheres to the protocol or program developed. During the last decades, assessment of fidelity has had an increasing significance for evaluations, treatment effectiveness research, and service administration [In clinical trials reporting on treatment interventions, the term treatment fidelity (TF) denotes the fidelity or integrity of an intervention [The intervention assessed in LongSTEP was a music therapy (MT) approach carried out in the context of neonatal intensive care units (NICUs) in different countries across Europe, the Middle East, and South America. With MT, we refer to “the informed use of music, facilitated by a trained music therapist within a therapeutic relationship, whereby engagement in musical processes serves as a resource to promote health” [The overall aim of this article is to report on TF in the LongSTEP trial, through evaluating the reliability of TF questionnaires developed for the trial, and the extent to which MT in the two intervention phases was a uniform intervention across therapists at the different research sites. Consistent with a pragmatic approach [