[Improving health care practices and organization: methodology for intervention studies]

Interventions designed to improve professional practices and healthcare organization are regularly implemented in all health systems. Their effectiveness on quality of care should be properly evaluated prior to their widespread implementation. Intervention studies can be conducted for this purpose according to a rigorous methodology in order to provide results with a good level of evidence. This article describes the main phases of an intervention study, including definition of the intervention, choice of study design, outcomes assessment, and writing of the report. It also addresses methodological issues of intervention studies designed to improve quality of care, such as cluster-randomization or the use of quasi-experimental designs. One of the specific features of these studies is that professionals are the targets, while patients are the beneficiaries of the intervention. A good knowledge of the specific features of studies designed to improve quality of care is essential to conduct research, or to evaluate the quality of the evidence from published studies.