Combining qualitative studies with randomised controlled trials is often useful

EDITOR,—Nick Black points out some of the limitations of randomised controlled trials but fails to mention that such trials rarely tell us why an intervention was successful or not.1 Pharmacological studies may provide this vital information for drug interventions, but for other interventions, especially those that involve packages of services, randomised controlled trials are unlikely to do so. Black suggests that we should be open to using alternative designs, but he specifically excludes qualitative methods from consideration. We believe that …