Developing quality fidelity and engagement measures for complex health interventions.

The five steps that we propose can be used to develop psychometrically robust and implementable measures of fidelity and engagement for complex health interventions that can be used by different target audiences. By considering quality when developing measures, we can be more confident in the interpretation of intervention outcomes drawn from fidelity and engagement studies. Statement of contribution What is already known on the subject? Fidelity and engagement can be measured using a range of methods, such as observation and self-report. Studies seldom report psychometric and implementation qualities of fidelity measures. What does this study add? A method for developing fidelity and engagement measures for complex health interventions. Guidance on how to consider quality when developing fidelity and engagement measures.