This two-study report investigates the equivalence of the Dutch Therapist Adherence Measure Revised (TAM-R) to the US original. The TAM-R is a questionnaire measuring therapist adherence to the treatment model of Multisystemic Therapy (MST). Monitoring of therapist adherence is essential for evidence-based interventions to ensure the quality of the delivered treatment. International implementation of the TAM-R assumes cross-national equivalence, even though this assumption has never been investigated. In study 1 Rasch analysis was applied to 1,875 Dutch TAM-R reports and the response category frequency distributions of the items of 1,875 US TAM-R reports. Response frequencies were more heavily skewed in the US compared to the Netherlands and several items showed Differential Item Functioning (DIF). Study 2 investigated whether adaptations to the translation of the items and response categories could improve equivalence. For this purpose, 237 families were randomly allocated to 1 of 3 versions (original TAM-R, adapted items only, adapted items and response categories) and the analyses from study 1 were replicated. Results indicated that equivalence was not improved by the adapted translations. The article concludes with a discussion of several potential other sources of bias, such as differences in sample characteristics, implementation of MST, and response styles.

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European Journal of Psychological Assessment
Department of Psychiatry

Lange, A.M.C. (Aurelie M.C.), Scholte, R., van Geffen, W., Timman, R., van Busschbach, J., & van der Rijken, R. (2016). The lack of cross-national equivalence of a therapist adherence measure (TAM-R) in multisystemic therapy (MST). European Journal of Psychological Assessment, 32(4), 312–325. doi:10.1027/1015-5759/a000262