Levels of Evidence

General

From the Centre for Evidence-Based Medicine, Oxford

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'

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TY - ELEC T1 - Levels of Evidence ID - 426001 ED - Barry,Henry, ED - Ebell,Mark H, ED - Shaughnessy,Allen F, ED - Slawson,David C, BT - EE+ POEM Archive UR - https://evidence.unboundmedicine.com/evidence/view/infoPOEMs/426001/all/Levels_of_Evidence PB - John Wiley & Sons DB - Evidence Central DP - Unbound Medicine ER -