Acceptability, reliability, and validity of a brief measure of capabilities, opportunities, and motivations ("COM-B")

Objectives: The Capabilities, Opportunities, Motivations and Behaviour (COM-B) model is being used extensively to inform intervention design, but there is no standard measure with which to test the predictive validity of COM or to assess the impact of interventions on COM. We describe the development, reliability, validity, and acceptability of a generic six-item self-evaluation COM questionnaire. Design and Methods: The questionnaire was formulated by behaviour change experts. Acceptability was tested in two independent samples of healthcare professionals (N=13 and N=85, respectively) and a sample of people with low socioeconomic status (N=214). Acceptability (missing data analyses and user feedback), reliability (test-retest reliability and Bland-Altman plots) and validity (floor and ceiling effects), Pearson's correlation coefficient [r], exploratory factor analysis and [EFA] and confirmatory factor analysis [CFA]) were tested using a national survey of 1,387 healthcare professionals. Results: The questionnaire demonstrated acceptability (missing data for individual items: 5.9% to 7.7% at baseline and 18.1%-32.5% at follow-up), reliability, (ICCs .554-.833), and validity (floor effects 0.6 – 5.5%, and ceiling effects 4.1 – 22.9%; pairwise correlations rs significantly<1.0). The regression models accounted for between 21% and 47% of the variance in behaviour. CFA (three-factor model) demonstrated a good model fit, (χ2[6] = 7.34, p = .29, RMSEA = .02, CFI = .99, TLI = .99, BIC = 13510.420, AIC = 13428.067). Conclusions: The novel six-item questionnaire shows evidence of acceptability, validity, and reliability for self-evaluating capabilities, opportunities, and motivations. Future research should aim use this tool in different populations to obtain further support for its reliability and validity.