Commentary on “A theory-based process evaluation alongside a randomised controlled trial of printed educational messages to increase primary care physicians’ prescription of thiazide diuretics for hypertension”

Commentary: In this research, the authors explored why an education-based intervention aimed at changing physicians’ prescribing behavior was ineffective. To answer this question, the authors used a theory-based process evaluation of the trial, employing the Theory of Planned Behavior (TPB). The authors hypothesized that the underlying theoretical mechanism of the intervention was that the intervention would affect change in prescribing behavior by changing intention, attitudes, and subjective norms (all TPB constructs). The theory-based process evaluation revealed that prior to the start of the intervention, clinicians already scored “high” on the TPB constructs (i.e., there was a ceiling effect of pre-existing strong intention, subjective norm, and positive attitude). As such, the theory-based evaluation provided an explanation of why the intervention was not effective at producing change on the TPB constructs and thus did not result in a change in the target behavior (physicians’ prescribing behavior). Regarding their intervention specifically, the authors concluded that educational materials may be ineffective at changing prescribing patterns when physicians’ pre-existing motivation to prescribe is strong. More generally, the authors suggest that conducting theory-based process evaluations concurrent with randomized trials of interventions may prove useful in interpreting results from pragmatic trials. In addition to this application, I would argue that theory-based surveys conducted prior to/as part of intervention design may also prove useful. For example, had the authors measured providers’ intention, attitudes and subjective norms prior to designing and testing the intervention, they may have identified the theory-based ‘ceiling effect’ earlier and could have adjusted their intervention design accordingly.

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