Cochrane Intervention reviews aim primarily to determine whether an intervention is effective compared with a control and, if so, to estimate the size of the effect. High quality randomized trials are central to the endeavours of The Cochrane Collaboration in this respect. It is neither appropriate nor possible to include evidence from qualitative research in all Cochrane reviews.
However, it is increasingly being recognized that evidence from qualitative studies that explore the experience of those involved in providing and receiving interventions, and studies evaluating factors that shape the implementation of interventions, have an important role in ensuring that systematic reviews are of maximum value to policy, practice and consumer decision-making (Mays 2005, Arai 2005, Popay 2005).
The relevance of qualitative evidence to the assessment of interventions has only recently received recognition in the health field, but it is now more common for qualitative components to be built into the evaluation of health interventions (Pope 2006) and for the evaluation of complex interventions such as differing models of health service delivery to use a ‘mixed methods’ approach. It is therefore increasingly likely that outcome studies included in Cochrane reviews will have qualitative research embedded within, or associated with, them. Authors of Cochrane reviews are therefore increasingly asking how to utilize evidence from qualitative research to enhance the relevance and utility of their review to potential users.
A synthesis of evidence from qualitative research can explore questions such as how do people experience illness, why does an intervention work (or not), for whom and in what circumstances? In some reviews, particularly those addressing healthcare delivery, it may be desirable to draw on qualitative evidence to address questions such as what are the barriers and facilitators to accessing health care, or what impact do specific barriers and facilitators have on people, their experiences and behaviours? These may be generated, for example, through ethnographies and interview studies of help-seeking behaviour. Evidence from qualitative research can help with interpretation of systematic review results by aiding understanding of the way in which an intervention is experienced by all of those involved in developing, delivering or receiving it; what aspects of the intervention they value, or not; and why this is so. These types of qualitative evidence can provide insight into factors that are external to an intervention including, for example, the impact of other policy developments, factors which facilitate or hinder successful implementation of a programme, service or treatment and how a particular intervention may need to be adapted for large-scale roll-out (Roen 2006).
We identify four ways in which qualitative research can contribute to Cochrane Intervention reviews for health policy and practice (Popay 2006a):
Informing reviews by using evidence from qualitative research to help define and refine the question. This ensures the review includes appropriate studies and addresses important outcomes, allowing the review to be of maximum relevance to potential users.
Enhancing reviews by synthesizing evidence from qualitative research identified whilst looking for evidence of effectiveness. Qualitative evidence associated with trials can be used to explore issues of implementation of the intervention. We consider qualitative research performed alongside randomized trials in more detail in Section 20.2.3.
Extending reviews by undertaking a search and synthesis specifically of evidence from qualitative studies to address questions directly related to the effectiveness review.
Supplementing reviews by synthesizing qualitative evidence to address questions on aspects other than effectiveness.
Qualitative syntheses for extending and supplementing reviews take either a multi-level or a parallel synthesis approach, as discussed in Section 20.3.2.5. No template is currently in place to allow a Cochrane review solely of qualitative evidence.
The Cochrane Public Health and Health Promotion field have produced additional guidance on the types of reviews and questions where qualitative research can add value (see Chapter 21). Such reviews are designed to answer the following questions: 1) does the intervention work (effectiveness), 2) why does it work or not work – including how does it work (feasibility, appropriateness and meaningfulness), and 3) how do participants experience the intervention?
Where qualitative research is used to enhance or extend a Cochrane Intervention review, methods for the specification, identification, critical appraisal and synthesis of qualitative research should be described under a separate heading under ‘Data collection and analysis’ in the Methods of the review.