• accreditation
• attitudes
• checklists

The years immediately following the widespread interest in patient safety1 and then healthcare quality2 saw considerable debate between pragmatically oriented improvers and research-oriented evaluators3–6 —or between ‘evangelists’ and ‘snails’ as one longtime observer characterised the two groups.7 Too often, enthusiastic improvers (‘evangelists’) relied on simple pre-post designs within a single context leading to erroneous claims of efficacy.8 In contrast, research-oriented investigators (‘snails’) and journals pushed for ever more rigorous designs including randomised trials, potentially at the cost of discouraging many improvers without this training and leading to slower development and deployment of effective interventions.9 10 Many clinicians, quality improvement (QI) experts and researchers are thus caught in a quandary: how best to evaluate a candidate QI intervention? How can we best balance the pragmatic needs of improvement—including the frequent need to refine the intervention or its implementation—with the requirement of most traditional evaluative designs, which typically require a static intervention?

We believe this question is one of the most important issues to consider when developing a QI intervention and is often not considered carefully enough—either by snails or evangelists. Decisions about when and how to evaluate potentially promising interventions can have crucial implications for the future of the intervention and the patients it could affect.