Background:
Narrative synthesis is a common synthesis method used to synthesise data when meta-analysis is not possible or appropriate. Around 50% of Cochrane Reviews use narrative synthesis for some or all of the data. In public health reviews, where there are often multiple sources of heterogeneity, narrative synthesis is frequently the main synthesis method. Despite this, narrative synthesis is often poorly reported, and the links between the data and the conclusions of the synthesis are often not transparent, and ultimately threatens the reliability and utility of reviews using narrative synthesis. The persistence of these problems may be partly explained by a lack of support or clear guidance to promote rigour in narrative synthesis, as well as a lack of familiarity with good practice in narrative synthesis, even among experienced review authors.

Objectives:
- To facilitate learning through experience about how to conduct a narrative synthesis for reviews where there are multiple sources of heterogeneity.
- To facilitate learning about the challenge of ensuring transparency and consistency in narrative synthesis for reviews where there are multiple sources of heterogeneity.

Description:
This workshop aims to complement the workshop 'Synthesis when meta-analysis is not possible (Part 1)', by providing an opportunity to work on an example with additional sources of heterogeneity. The workshop will start with a presentation on the principles and challenges of narrative synthesis for reviews of complex interventions where there are multiple sources of heterogeneity, and provide a summary of tools to promote transparency in narrative synthesis. Participants will then have the opportunity to trial the knowledge gained in the presentation. Participants will be provided with extracted and tabulated data from a published Cochrane Review of a public health intervention, and will be asked to prepare a brief narrative synthesis of one or more outcomes. Small group discussion will feed into a final discussion with the whole group about the issues in preparing a narrative, including promoting transparency and replicability.