Enhancing treatment fidelity in psychotherapy research: novel approach to measure the components of cognitive behavioural therapy for relapse prevention in first-episode psychosis.

Objectives: Establishing treatment fidelity is one of the most important aspects of psychotherapy research. Treatment fidelity refers to the methodological strategies used to examine and enhance the reliability and validity of psychotherapy. This study sought to develop and evaluate a measure specifically designed to assess fidelity to the different therapeutic components (i.e. therapy phases) of the individual intervention of a psychotherapy clinical trial (the EPISODE II trial).

Method: A representative sample of sessions stratified by therapy phase was assessed using a specifically developed fidelity measure (Relapse Prevention Therapy-Fidelity Scale, RPT-FS). Each RPT-FS subscale was designed to include a different component/phase of therapy and its major therapeutic ingredients.

Results: The measure was found to be reliable and had good internal consistency. The RPT-FS discriminated, almost perfectly, between therapy phases. The analysis of the therapeutic strategies implemented during the intervention indicated that treatment fidelity was good throughout therapy phases. While therapists primarily engaged in interventions from the appropriate therapeutic phase, flexibility in therapy was evident.

Conclusions: This study described the development of a brief, reliable and internally consistent measure to determine both treatment fidelity and the therapy components implemented throughout the intervention. This methodology can be potentially useful to determine those components related to therapeutic change.