Synthesizing Qualitative Data Sets to Improve the Design of Trials and Complex Health Interventions: A Worked Example

Qualitative researchers are increasingly reanalyzing and synthesizing data sets from different studies, and this method has now been used across trials to inform trial methodology and delivery. Despite this work, however, limited guidance exists about how this method should be employed. This article details an example in which interview data collected during three primary care depression trials were brought together to explore trial participants' study and treatment journeys. It details the process involved and the decisions made. It also presents findings from this synthesis to illustrate how this method can be used to inform the development of future trials and complex interventions, through raising questions about how researchers currently define and design treatment arms and indicating what factors may improve or hinder participants' engagement with their allocated treatment.