• Patient safety
• Quality improvement
• Clinical practice guidelines

‘This safety stuff, it's not rocket science’. Many readers of this journal will undoubtedly have heard this sentiment expressed by their clinical colleagues. The article by Kemper et al1 shows just how widely this impression of patient safety misses the mark. This high-quality study confirms the trend of the recent literature by finding that teamwork training using the civil aviation Crew Resource Management (CRM) approach has no evident clinical benefit, although it does seem to change attitudes and enhance some aspects of the ‘non-technical’ skills involved with interacting with colleagues. In doing so, the study highlights three areas of complexity and challenge in the development and evaluation of safety interventions. First, the interventions themselves are deceptively complex; as recommended by experts, they are grounded in theory,2 but may be entirely wrong. Second, the success of even ‘simple’ interventions like the WHO checklist hugely depends on the context and the implementation strategy. And third, the act of evaluation is far more difficult than it might first appear.

Let us start from the end. By the methodological standards of safety and quality intervention studies generally, this is an exceptionally well done study. It is sizeable, involving six hospitals and over 8000 patients. There is a clear ‘PICO’ question as recommended by evidence-based medicine (EBM) pundits; the study protocol was published in advance; the study uses mixed methods intelligently to study outcomes in a structured way, using Kirkpatrick's educational model; and there is even a control group.

As a practitioner in the same field, the writer salutes the study group for their thorough and thoughtful approach. Yet, by the exacting standards of EBM, even this study would be regarded as being at moderate-to-high risk of bias. The allocation to groups is not random—intervention hospitals needed to sign up to certain financial …