20.2.3  Considering qualitative studies that are identified within, or alongside, randomized controlled trials.

As ‘mixed methods’ evolve to evaluate the effects of complex interventions such as health service delivery strategies, it is increasingly likely that studies included in Cochrane Intervention reviews will have qualitative research embedded within or associated with them, although the evidence resulting from the qualitative studies may not be reported in the same publication as that of the trial. For example, in an exemplar review we summarize in Box 20.3.a, five out of six trials included in the Cochrane Intervention review had a qualitative component or associated study, although not all qualitative data had been analysed or published. Importantly, this qualitative component was not always referenced in the trial report. Indeed some studies only came to light after making contact with the trial principal investigator.


When considering qualitative research identified within or alongside randomized trials, the following issues need to be considered:

  1. Identification of qualitative evidence: Qualitative evidence retrieved using a topic-based search strategy designed to identify trials cannot be viewed as being either comprehensive or representative. Such a search strategy is not designed for the purpose of identifying qualitative studies and indeed achieves a measure of specificity by purposefully excluding many qualitative research types.

  2. Qualitative evidence synthesis to explore the experience of having the disease: If the experience of the disease is the focus of interest then qualitative sources identified from the trial search strategy will not necessarily provide a holistic or comprehensive view. In these cases a multilevel or parallel synthesis should be considered or facilitated (see Section Ideally an author would work with a qualitative researcher and information specialist to develop a qualitative search strategy to identify other relevant studies.

  3. Qualitative synthesis to explore issues of implementation of the intervention: If issues surrounding implementation are the focus of interest then qualitative evidence embedded within or associated with the trials would be most relevant. Such implementation evidence is most likely to be generated by mixed methods research and to include both qualitative and quantitative evidence. Steps need to be taken to identify all qualitative sources associated with the trials, such as undertaking additional targeted searching and contacting the trial principal investigator.

  4. Considering qualitative evidence within studies excluded from Cochrane Intervention reviews: There may be occasions when a trial does not meet the eligibility criteria for a Cochrane Intervention review (for example due to unacceptable risk of bias) but the qualitative research embedded within or accompanying the trial is considered high quality. The guiding principle follows that if the qualitative evidence appears robust, the qualitative evidence can be incorporated into the review.