McAndrews, Richardson, & Stopa. 2019

Acceptance is an important construct across models for understanding psychological distress. Several measures have been designed to capture this, however, there is a lack of evidence regarding the most suitable tool. The objective of this review was to systematically evaluate measurement properties of tools designed to measure self-reported acceptance. A systematic review of the literature on psychometric properties of acceptance measures was performed. Articles were selected if the primary aim was to develop or evaluate measurement properties (validity, reliability, responsiveness) of a self-report acceptance scale (or subscale). The methodological quality of included studies was evaluated using the COnsensus-based Standards for the selection of health status Measurement INstruments (COSMIN) checklist. The quality of measurement properties were evaluated using criteria suggested by Terwee et al. (2007). All studies were independently reviewed by two raters, and inter-rater reliability was assessed. The search strategy identified 3097 unique articles. Twenty articles, reporting 32 studies, met inclusion criteria. Nine instruments were identified; two unidimensional scales of acceptance, four mindfulness tools with an acceptance subscale, and three emotion regulation scales with an acceptance-based subscale. None of the instruments were assessed across all domains of psychometric properties. No studies investigated measurement error or cross-cultural validity. Internal consistency was the most widely assessed property, and was generally acceptable across all scales. Lack of target population involvement resulted in poor content validity for most scales. Inter-rater reliability of study selection and evaluation was excellent. There are important conceptual differences across current acceptance measures, which might result from differences in theoretical models on which these are based. None of the measures evaluated can be recommended as having superior psychometric properties. Important limitations in content validity need to be addressed, with greater involvement of target populations. Further research is required to demonstrate the psychometric properties of existing measures, given their significant role in evaluating acceptance-based interventions across clinical and research settings.

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