OBJECTIVE: Assessing treatment fidelity in effectiveness research is critical to interpreting study findings. This paper details the development and initial psychometric evaluation of the Modular Evidence-Based Practices for Youth with Autism Fidelity Scale (MEYA-FS) designed to support the assessment of cognitive-behavioral treatments for youth with autism in effectiveness research. METHOD: Recorded treatment sessions ( = 338) were randomly selected from 77 youth ( age = 9.65 years, = 1.87; 50.67% White; 85.33% male) who received the Schema, Emotion, and Behavior-Focused Therapy for Children (SEBASTIEN) ( = 51) or Coping Cat ( = 24) program. RESULTS: The MEYA-FS Adherence items displayed acceptable interrater reliability, but more than half of the MEYA-FS Competence items did not. The magnitude and pattern of correlations supported the score validity of the MEYA-FS Adherence and Competence items and subscales. However, some corresponding Adherence and Competence items displayed significant overlap. Scores on each Adherence subscale distinguished between the SEBASTIEN and Coping Cat programs, providing support for discriminant validity. Finally, higher Adherence and Competence subscales predicted significant improvements in youth clinical outcomes (adjustment problems in the school setting, social-communication difficulties, restrictive/repetitive behaviors, and externalizing problems), providing initial evidence for predictive validity. CONCLUSIONS: The psychometric properties of the MEYA-FS make it appropriate for supporting efforts to evaluate cognitive-behavioral interventions for youth with autism in effectiveness and implementation research.
