The effect direction plot revisited: application of the 2019 Cochrane Handbook guidance on alternative synthesis methods

Hilton Boon, M. and Thomson, H. (2021) The effect direction plot revisited: application of the 2019 Cochrane Handbook guidance on alternative synthesis methods. Research Synthesis Methods, 12(1), pp. 29-33. (doi: 10.1002/jrsm.1458) (PMID:32979023) (PMCID:PMC7821279)

Abstract

Effect direction (evidence to indicate improvement, deterioration, or no change in an outcome) can be used as a standardized metric which enables the synthesis of diverse effect measures in systematic reviews. The effect direction (ED) plot was developed to support the synthesis and visualization of effect direction data. Methods for the ED plot require updating in light of new Cochrane guidance on alternative synthesis methods. To update the ED plot, statistical significance was removed from the algorithm for within‐study synthesis and use of a sign test was considered to examine whether patterns of ED across studies could be due to chance alone. The revised methods were applied to an existing Cochrane review of the health impacts of housing improvements. The revised ED plot provides a method of data visualization in synthesis without meta‐analysis that incorporates information about study characteristics and study quality, using ED as a common metric, without relying on statistical significance to combine outcomes of single studies. The results of sign tests, when appropriate, suggest caution in over‐interpreting apparent patterns in effect direction, especially when the number of included studies is small. The revised ED plot meets the need for alternative methods of synthesis and data visualization when meta‐analysis is not possible, enabling a transparent link between the data and conclusions of a systematic review. ED plots may be particularly useful in reviews that incorporate nonrandomized studies, complex systems approaches, and diverse sources of evidence, due to the variety of study designs and outcomes in such reviews.

• Item Type: Articles
• Additional Information: This work was supported by the UK Medical Research Council (grant number MC_UU_12017/15) and Scottish Government Chief Scientist Office (grant number SPHSU15).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Thomson, Dr Hilary and Hilton Boon, Dr Michele
• Authors: Hilton Boon, M., and Thomson, H.
• College/School: College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > MRC/CSO SPHSU
• Journal Name: Research Synthesis Methods
• Publisher: Wiley
• ISSN: 1759-2879
• ISSN (Online): 1759-2887
• Published Online: 26 September 2020
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in Research Synthesis Methods 12(1): 29-33
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
72767	1	Informing Healthy Public Policy	Peter Craig	Medical Research Council (MRC)	MC_UU_12017/15	HW - MRC/CSO Social and Public Health Sciences Unit
72767	1	Informing Healthy Public Policy	Peter Craig	Office of the Chief Scientific Adviser (CSO)	SPHSU15	HW - MRC/CSO Social and Public Health Sciences Unit