Grading the strength of a body of evidence when comparing medical interventions—Agency for Healthcare Research and Quality and the Effective Health Care Program
Accepted 11 March 2009. published online 13 July 2009. Corrected Proof
Abstract
Objective
To establish guidance on grading strength of evidence for the Evidence-based Practice Center (EPC) program of the U.S. Agency for Healthcare Research and Quality.
Study Design and Setting
Authors reviewed authoritative systems for grading strength of evidence, identified domains and methods that should be considered when grading bodies of evidence in systematic reviews, considered public comments on an earlier draft, and discussed the approach with representatives of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) working group.
Results
The EPC approach is conceptually similar to the GRADE system of evidence rating; it requires assessment of four domains: risk of bias, consistency, directness, and precision. Additional domains to be used when appropriate include dose–response association, presence of confounders that would diminish an observed effect, strength of association, and publication bias. Strength of evidence receives a single grade: high, moderate, low, or insufficient. We give definitions, examples, mechanisms for scoring domains, and an approach for assigning strength of evidence.
Conclusion
EPCs should grade strength of evidence separately for each major outcome and, for comparative effectiveness reviews, all major comparisons. We will collaborate with the GRADE group to address ongoing challenges in assessing the strength of evidence.
aVA Palo Alto Healthcare System, Palo Alto, CA, 94304 USA
bStanford-UCSF Evidence-based Practice Center, Stanford University, Stanford, CA, USA
cCenter for Primary Care and Outcomes Research, Stanford University, Palo Alto, CA, USA
dRTI International, Research Triangle Park, NC, 27709-2194 USA
eQuality Enhancement Research Initiative, Health Services Research & Development Service (HSR&D), Department of Veterans Affairs, Washington, DC, 20420 USA
fECRI Institute Evidence-based Practice Center, Plymouth Meeting, PA, 19462 USA
gJohns Hopkins University Evidence-based Practice Center, Baltimore, MD, 21287 USA
hCenter for Outcomes and Evidence, Agency for Healthcare Research and Quality, Rockville, MD, 20850 USA
iOregon Health & Sciences University Evidence-based Practice Center, Oregon Health & Sciences University, Staff Physician, Portland VA Medical Center, Portland, OR, 97207 USA
Corresponding author. Center for Primary Care and Outcomes Research, Stanford University, 117 Encina Commons, Stanford, CA 94305-6019, USA. Tel.: 650-723-0933; fax: 650-724-5182.
ABSTRACT