Evidence Ratings
Strength-of-Recommendation Taxonomy (SORT)
Code Definition A Consistent, good-quality patient-oriented evidence * B Inconsistent or limited-quality patient-oriented evidence * C Consensus, disease-oriented evidence *, usual practice, expert opinion, or case series for studies of diagnosis, treatment, prevention, or screening
- Patient-oriented evidence measures outcomes that matter to patients: morbidity, mortality, symptom improvement, cost reduction, and quality of life. Disease-oriented evidence measures immediate, physiologic, or surrogate end points that may or may not reflect improvements in patient outcomes (e.g. blood pressure, blood chemistry, physiologic function, pathologic findings).
Grading of Recommendations Assessment, Development and Evaluation (GRADE)
Code Quality of Evidence Definition A High Further research is very unlikely to change our confidence in the estimate of effect.
Several high-quality studies with consistent results In special cases: one large, high-quality multi-centre trial B Moderate Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
One high-quality study Several studies with some limitations C Low Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
One or more studies with severe limitations D Very Low Any estimate of effect is very uncertain.
Expert opinion No direct research evidence One or more studies with very severe limitations Source: GRADE (Grading of Recommendations Assessment, Development and Evaluation) Working Group 2007 1 (modified by the EBM Guidelines Editorial Team)
Centre for Evidence-Based Medicine
Oxford For the most up-to-date levels of evidence, see www.cebm.net/?o=1025
Practice guidelines scales (various)
Therapy/Prevention/Etiology/Harm: 1a: Systematic reviews (with homogeneity ) of randomized controlled trials 1a-: Systematic review of randomized trials displaying worrisome heterogeneity 1b: Individual randomized controlled trials (with narrow confidence interval) 1b-: Individual randomized controlled trials (with a wide confidence interval) 1c: All or none randomized controlled trials 2a: Systematic reviews (with homogeneity) of cohort studies 2a-: Systematic reviews of cohort studies displaying worrisome heterogeneity 2b: Individual cohort study or low quality randomized controlled trials (<80% follow-up) 2b-: Individual cohort study or low quality randomized controlled trials (<80% follow-up / wide confidence interval) 2c: 'Outcomes' Research; ecological studies 3a: Systematic review (with homogeneity) of case-control studies 3a-: Systematic review of case-control studies with worrisome heterogeneity 3b: Individual case-control study 4: Case-series (and poor quality cohort and case-control studies) 5: Expert opinion without explicit critical appraisal, or based on physiology, bench research or 'first principles' Diagnosis: 1a: Systematic review (with homogeneity) of Level 1 diagnostic studies; or a clinical rule validated on a test set. 1a-: Systematic review of Level 1 diagnostic studies displaying worrisome heterogeneity 1b: Independent blind comparison of an appropriate spectrum of consecutive patients, all of whom have undergone both the diagnostic test and the reference standard; or a clinical decision rule not validated on a second set of patients 1c: Absolute SpPins And SnNouts (An Absolute SpPin is a diagnostic finding whose Specificity is so high that a Positive result rules-in the diagnosis. An Absolute SnNout is a diagnostic finding whose Sensitivity is so high that a Negative result rules-out the diagnosis). 2a: Systematic review (with homogeneity) of Level >2 diagnostic studies 2a-: Systematic review of Level >2 diagnostic studies displaying worrisome heterogeneity 2b: Any of: 1)independent blind or objective comparison; 2)study performed in a set of non-consecutive patients, or confined to a narrow spectrum of study individuals (or both) all of whom have undergone both the diagnostic test and the reference standard; 3) a diagnostic clinical rule not validated in a test set. 3a: Systematic review (with homogeneity) of case-control studies 3a-: Systematic review of case-control studies displaying worrisome heterogeneity 4: Any of: 1)reference standard was unobjective, unblinded or not independent; 2) positive and negative tests were verified using separate reference standards; 3) study was performed in an inappropriate spectrum of patients. 5: Expert opinion without explicit critical appraisal, or based on physiology, bench research or 'first principles' Prognosis: 1a: Systematic review (with homogeneity) of inception cohort studies; or a clinical rule validated on a test set. 1a-: Systematic review of inception cohort studies displaying worrisome heterogeneity 1b: Individual inception cohort study with > 80% follow-up; or a clinical rule not validated on a second set of patients 1c: All or none case-series 2a: Systematic review (with homogeneity) of either retrospective cohort studies or untreated control groups in RCTs. 2a-: Systematic review of either retrospective cohort studies or untreated control groups in RCTs displaying worrisome heterogeneity 2b: Retrospective cohort study or follow-up of untreated control patients in an RCT; or clinical rule not validated in a test set. 2c: 'Outcomes' research 4: Case-series (and poor quality prognostic cohort studies) 5: Expert opinion without explicit critical appraisal, or based on physiology, bench research or 'first principles'
Key to interpretation of practice guidelines Agency for Healthcare Research and Quality: A: There is good research-based evidence to support the recommendation. B: There is fair research-based evidence to support the recommendation. C: The recommendation is based on expert opinion and panel consensus. X: There is evidence of harm from this intervention. USPSTF Guide to Clinical Preventive Services: A: There is good evidence to support the recommendation that the condition be specifically considered in a periodic health examination. B: There is fair evidence to support the recommendation that the condition be specifically considered in a periodic health examination. C: There is insufficient evidence to recommend for or against the inclusion of the condition in a periodic health examination, but recommendations may be made on other grounds. D: There is fair evidence to support the recommendation that the condition be excluded from consideration in a periodic health examination. E: There is good evidence to support the recommendation that the condition be excluded from consideration in a periodic health examination. University of Michigan Practice Guideline: A: Randomized controlled trials. B: Controlled trials, no randomization. C: Observational trials. D: Opinion of the expert panel. Other guidelines: A: There is good research-based evidence to support the recommendation. B: There is fair research-based evidence to support the recommendation. C: The recommendation is based on expert opinion and panel consensus. X: There is evidence that the intervention is harmful.
