The effect direction plot: visual display of non-standardised effects across multiple outcome domains

Abstract

Visual display of reported impacts is a valuable aid to both reviewers and readers of systematic reviews. Forest plots are routinely prepared to report standardised effect sizes, but where standardised effect sizes are not available for all included studies a forest plot may misrepresent the available evidence. Tabulated data summaries to accompany the narrative synthesis can be lengthy and inaccessible. Moreover, the link between the data and the synthesis conclusions may be opaque. This paper details the preparation of visual summaries of effect direction for multiple outcomes across 29 quantitative studies of the health impacts of housing improvement. A one page summary of reported health outcomes was prepared to accompany a 10 000-word narrative synthesis. The one page summary included details of study design, internal validity, sample size, time of follow-up, as well as changes in intermediate outcomes, for example, housing condition. This approach to visually summarising complex data can aid the reviewer in cross-study analysis and improve accessibility and transparency of the narrative synthesis where standardised effect sizes are not available. Copyright © 2012 John Wiley & Sons, Ltd.

Keywords: data tabulation; multiple outcomes; narrative synthesis; non-statistical heterogeneity.