Never mind the qualitative feel the depth! The evolving role of qualitative research in Cochrane intervention reviews

Whilst the Cochrane intervention review remains the gold standard, the previous focus on randomised controlled trials and exclusion of other types of evidence limited their utility for some users - especially policy makers and commissioners of services who had to draw on other types of evidence about patient views and context in order to make decisions. This paper reports a significant development in the evolution of the Cochrane intervention review and outlines an evolving role for qualitative evidence. Policy and methodological developments within the Cochrane Collaboration and beyond will be discussed alongside an ongoing debate about the politics of evidence and perceived power of the quantitative effectiveness review in an evidence-based practice context. The paper concludes with six key messages, including: (1) the Cochrane Collaboration has consistently acknowledged the potential value of qualitative evidence; (2) Cochrane was an early leader in quantitative evidence synthesis and developed a gold standard approach for effectiveness reviews; (3) early leaders in the field tend to dominate until other approaches are developed, tested and evaluated to challenge early leader dominance; (4) other review organisations and individuals have now developed expertise in qualitative and mixed method synthesis and there is an emerging and developing evidence base with a range of qualitative synthesis approaches for different contexts; (5) there is still a need for further methodological development, testing and evaluation, and (6) finally, more than one hierarchy of evidence is needed to address different types of questions, and the dominance and application of one hierarchy to all contexts is unhelpful and counterintuitive to achieving evidence-based healthcare.