George A Wells1,2, Beverley Shea3, Julian Pt Higgins4,5, Jonathan Sterne6, Peter Tugwell2,7, Barnaby C Reeves8. 1. Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Canada. 2. Department of Medicine, University of Ottawa, Ottawa, Canada. 3. Community Information and Epidemiological Technologies, Institute of Population Health, Ottawa, Canada. 4. MRC Biostatistics Unit, Cambridge, UK. 5. Centre for Reviews and Dissemination, University of York, York, UK. 6. School of Social and Community Medicine, University of Bristol, UK. 7. Centre for Global Health, Institute of Population Health, Ottawa, Canada. 8. Clinical Trials and Evaluation Unit, School of Clinical Sciences, University of Bristol, UK.
Abstract
BACKGROUND: There is increasing interest from review authors about including non-randomized studies (NRS) in their systematic reviews of health care interventions. This series from the Ottawa Non-Randomized Studies Workshop consists of six papers identifying methodological issues when doing this. AIM: To format the guidance from the preceding papers on study design and bias, confounding and meta-analysis, selective reporting, and applicability/directness into checklists of issues for review authors to consider when including NRS in a systematic review. CHECKLISTS: Checklists were devised providing frameworks to describe/assess: (1) study designs based on study design features; (2) risk of residual confounding and when to consider meta-analysing data from NRS; (3) risk of selective reporting based on the Cochrane framework for detecting selective outcome reporting in trials but extended to selective reporting of analyses; and (4) directness of evidence contributed by a study to aid integration of NRS findings into summary of findings tables. SUMMARY: The checklists described will allow review groups to operationalize the inclusion of NRS in systematic reviews in a more consistent way. The next major step is extending the existing Cochrane Risk of Bias tool so that it can assess the risk of bias to NRS included in a review.
BACKGROUND: There is increasing interest from review authors about including non-randomized studies (NRS) in their systematic reviews of health care interventions. This series from the Ottawa Non-Randomized Studies Workshop consists of six papers identifying methodological issues when doing this. AIM: To format the guidance from the preceding papers on study design and bias, confounding and meta-analysis, selective reporting, and applicability/directness into checklists of issues for review authors to consider when including NRS in a systematic review. CHECKLISTS: Checklists were devised providing frameworks to describe/assess: (1) study designs based on study design features; (2) risk of residual confounding and when to consider meta-analysing data from NRS; (3) risk of selective reporting based on the Cochrane framework for detecting selective outcome reporting in trials but extended to selective reporting of analyses; and (4) directness of evidence contributed by a study to aid integration of NRS findings into summary of findings tables. SUMMARY: The checklists described will allow review groups to operationalize the inclusion of NRS in systematic reviews in a more consistent way. The next major step is extending the existing Cochrane Risk of Bias tool so that it can assess the risk of bias to NRS included in a review.
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