Subgroup analyses in systematic reviews: A survey of Cochrane and non-Cochrane reviews

Abstract text
Background: Studies included in a meta-analysis often differ in methodological, patient, and intervention characteristics, and outcome measures, differences that may result in heterogeneity of treatment effects. Subgroup analyses may explain such heterogeneity. However, both inappropriate conduct and reporting of subgroup analyses may lead to misguided clinical and policy decisions, and the extent to which systematic review authors undertake subgroup analyses and the quality of their conduct and reporting remain uncertain.

Objective: To examine the extent to which subgroup analyses are conducted, and to compare the quality of conduct and reporting of subgroup analyses between Cochrane versus non-Cochrane reviews.

Methods: We searched the Cochrane Database of Systematic Reviews and the Medline for systematic reviews published in 2010 that included a meta-analysis of dichotomous outcome reported in randomized controlled trials. Teams of two reviewers screened studies for eligibility. We randomly selected 75 Cochrane and 75 non-Cochrane reviews from eligible studies. Teams of two reviewers are currently abstracting data using standardized, piloted forms guided with written instructions

We will focus on subgroup analyses of aggregate data meta-analyses, and the unit of analysis is an individual systematic review. Our analysis will examine whether authors planned to explore heterogeneity, whether they were able to explore heterogeneity, reasons for the failure of exploring heterogeneity, and approaches to exploring heterogeneity. We will examine whether a subgroup hypothesis was pre-specified, the number of subgroup hypotheses tested, the number of outcomes and corresponding effect measures used for subgroup analyses, and whether a test of interaction was used. For each major issue, we will compare practice in Cochrane versus non-Cochrane reviews.

Results: The results of analyses will be available for presentation at the colloquium.

Discussion: The results of this study will provide an important insight about the quality of conduct and reporting of subgroup analyses in systematic reviews.

Sun X1, Brignardello-Petersen R2, Carrasco-Labra A2, Neumann I3, Alonso-Coello P4, Akl E5, Johnston B6, Briel M7, Busse J8, Dahm P9, Granados C4, Glujovsky D10, Iorio A8, Irfan A11, Martinez L4, Reem Mustafa RM8, Ramirez-Morera A12, Solá I4, Sultan S13, Tikkinen K14, Vandvik P15, Zhang M4, Guyatt G4
1 Centre for Health Research, Kaiser Permanente Northwest, Portland, Oregon
2 Evidence Based Dentistry Unit, Faculty of Dentistry, Universidad de Chile, Chile
3 Department of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
4 Iberoamerican Cochrane Centre. Institute of Biomedical Research (IIB Sant Pau) Barcelona, Spain
5 Department of Medicine, State University of New York at Buffalo, NY, USA
6 Research Institute, Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Canada
7 Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Switzerland
8 Department of Clinical Epidemiology & Biostatistics, McMaster University, Canada
9 Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, USA
10 Argentine Cochrane Centre IECS (Institute for Clinical Effectiveness and Health Policy), Buenos Aires, Argentina
11 Internal Medicine Residency Program, University of Illinois at Urbana-Champaign, USA
12 CCSS Permanent Medical Advisor, Health Care Development Division. IHCAI FOUNDATION & Central America Cochrane branch associated fellow, Costa Rica.
13 Division of Gastroenterology, Hepatology, and Nutrition, Malcom Randall Veterans Affairs Medical Center, University of Florida College of Medicine
14 Dept. of Urology, Helsinki University Central Hospital, Helsinki, Finland
15 Norwegian Knowledge Centre for the Health Services, Oslo, Norway
Presenting author and contact person
Presenting author: 
Gordon Guyatt
Contact person Affiliation Country
Bradley Johnston (Contact this person) Clinical Epidemiology & Biostatistics, McMaster, Ontario Canada
Date and Location
Oral session C16O3
Wednesday 3 October 2012 - 11:40 - 12:00