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Table 2 Criteria for recommendation grading

From: A critical appraisal of guidelines for the management of knee osteoarthritis using Appraisal of Guidelines Research and Evaluation criteria

Ottawa Panel [11]
A Evidence from one or more randomized controlled trials of a statistically significant, clinically important benefit (>15%)
B Statistically significant, clinically important benefit (>15%) if the evidence is from observational studies or controlled clinical trials
C+ Clinical importance (>15%) but no statistical significance
C No clinically important difference and no statistical significance
D Evidence from one or more randomized controlled trials of a statistically significant benefit favouring the control group
Canadian Consensus Conference [8] and European League Against Rheumatism [6]
A Meta-analysis of randomized controlled trial or at least one randomized controlled trial
B At least one controlled study without randomization or at least one quasi-experimental study
C Descriptive studies, such as comparative, correlation or case–control studies
D Expert committee reports or opinions and/or clinical experience of respected authorities
American Academy of Orthopaedic Surgeons [10]
A Meta-analysis of multiple, well-designed controlled studies; or high-power randomized, controlled clinical trial; or consistent findings from multiple well-designed experimental studies; or low-power randomized, controlled clinical trials; or nonexperimental studies such as nonrandomized, controlled single-group, pre–post, cohort, time, or matched case–control series; or nonexperimental studies, such as comparative and correlational descriptive and case studies
B Generally consistent findings from well-designed experimental studies; or low-power randomized, controlled clinical trials; or nonexperimental studies such as nonrandomized, controlled single-group, pre–post, cohort, time, or matched case–control series; or nonexperimental studies, such as comparative and correlational descriptive and case studies
C Inconsistent findings from well-designed experimental studies; or low-power randomized, controlled clinical trials; or nonexperimental studies such as nonrandomized, controlled single-group, pre–post, cohort, time, or matched case–control series; or nonexperimental studies, such as comparative and correlational descriptive and case studies
D Little or no systematic empirical evidence
Institute for Clinical Systems Improvement [9]
1 Strong design study results that are clinically important and consistent. The results are free of any significant doubts about generalizability, bias, and flaws in research design. Studies with negative results have sufficiently large samples to have adequate statistical power
2 Strong design study results that are inconsistent or with minor doubts about generalizability, bias, flaws in research design, or adequacy of sample size. Alternatively, evidence consists solely of consistent results from weaker designs
3 Strong design study results that are substantially inconsistent or with serious doubts about generalizability, bias, flaws in research design, or adequacy of sample size. Alternatively, evidence consists solely of limited results from weaker designs