BMJ Global Health: Synthesising quantitative and qualitative evidence to inform guidelines on complex interventions

14 December, 2019

Below are the citation and summary points of a new article in BMJ Global Health, and a comment from me below. Full text here:

CITATION: Noyes J, Booth A, Moore G, et al. Synthesising quantitative and qualitative evidence to inform guidelines on complex interventions: clarifying the purposes, designs and outlining some methodsBMJ Global Health 2019;4:e000893.


Guideline developers are increasingly dealing with more difficult decisions concerning whether to recommend complex interventions in complex and highly variable health systems. There is greater recognition that both quantitative and qualitative evidence can be combined in a mixed-method synthesis and that this can be helpful in understanding how complexity impacts on interventions in specific contexts. This paper aims to clarify the different purposes, review designs, questions, synthesis methods and opportunities to combine quantitative and qualitative evidence to explore the complexity of complex interventions and health systems. Three case studies of guidelines developed by WHO, which incorporated quantitative and qualitative evidence, are used to illustrate possible uses of mixed-method reviews and evidence. Additional examples of methods that can be used or may have potential for use in a guideline process are outlined. Consideration is given to the opportunities for potential integration of quantitative and qualitative evidence at different stages of the review and guideline process. Encouragement is given to guideline commissioners and developers and review authors to consider including quantitative and qualitative evidence. Recommendations are made concerning the future development of methods to better address questions in systematic reviews and guidelines that adopt a complexity perspective.

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- When combined in a mixed-method synthesis, quantitative and qualitative evidence can potentially contribute to understanding how complex interventions work and for whom, and how the complex health systems into which they are implemented respond and adapt.

- The different purposes and designs for combining quantitative and qualitative evidence in a mixed-method synthesis for a guideline process are described.

- Questions relevant to gaining an understanding of the complexity of complex interventions and the wider health systems within which they are implemented that can be addressed by mixed-method syntheses are presented.

- The practical methodological guidance in this paper is intended to help guideline producers and review authors commission and conduct mixed-method syntheses where appropriate.

- If more mixed-method syntheses are conducted, guideline developers will have greater opportunities to access this evidence to inform decision-making.

COMMENT (NPW): I have not been able to study this paper in depth but one aspect that it does not seem to address is the synthesis of global and local/national evidence. I am not at all an expert in this field, but it seems to me that improving methods of, and support for, such synthesis, is key, especially in 'complex and highly variable health systems'. Are you aware of methods to do this?

Best wishes, Neil

Coordinator, HIFA Project on Evidence-Informed Policy and Practice

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