The choice of method for inclusion of qualitative evidence in a qualitative evidence synthesis will depend on a number of factors, including the:
type and scope of the review and review question(s);
pool of available evidence;
expertise of the team; and
available resources.
There are a number of evolving methods for the synthesis of qualitative and mixed-method evidence. Along with other interested individuals and systematic review organizations, Cochrane Qualitative Research Methods Group members are actively involved in developing and more recently beginning to evaluate the range of methods available. Members have contributed to two core texts on synthesizing qualitative and quantitative health evidence, which provide more detailed information and guidance on methods and processes (Petticrew 2006, Pope 2007).
We recommend that any high quality method of qualitative evidence synthesis may be used that is best suited to the type of Intervention review.
It is beyond the scope of the chapter to include detailed description of the range of methods available for qualitative and mixed-method evidence synthesis. A variety of methods have been used in published reviews. Examples include: Bayesian meta-analysis, critical interpretive synthesis, Evidence for Policy and Practice Information (EPPI) Coordinating Centre approach, Joanna Briggs Institute (JBI) approach, meta-ethnography, meta-synthesis, meta-study, meta-summary, narrative synthesis, qualitative evidence synthesis drawing on grounded theory, realist synthesis, and secondary thematic analysis.
Most methods have associated detailed guidance (see for example Noblit and Hare on meta-ethnography and Popay et al. on narrative synthesis (Noblit 1988, Popay 2006b)), which should be referred to. Dixon-Woods et al. provide a detailed overview of the potential of several methods and associated challenges (Dixon-Woods 2005, Dixon-Woods 2006). As yet, little evaluation has been undertaken to determine the robustness of different methods. Further reading can be found in Section 20.6