Table 1 |
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The Oxford Centre for Evidence-based Medicine Levels of Evidence. |
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| Level |
Therapy |
Diagnosis |
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| 1a |
Systematic review (SR) of Randomised Clinical Trials (RCT) |
SR of Level 1 diagnostic studies; Clinical Decision Rule (CDR) with 1b studies from different clinical centres. |
| 1b |
Individual RCT (with narrow confidence interval) |
Validating cohort study with good reference standards, or CDR tested within one clinical centre. |
| 1c |
All or none†† |
Diagnostic finding whose specificity is so high that a positive result rules-in the diagnosis. Diagnostic finding whose Sensitivity is so high that a Negative result rules-out the diagnosis. |
| 2a |
SR of cohort studies |
SR of Level 2a-c diagnostic studies |
| 2b |
Individual cohort study (including low-quality RCT; e.g., follow-up of <80% of patients) |
Exploratory cohort study with good reference standards; CDR after derivation, or validated only on split-sample or databases |
| 2c |
Audits or "outcomes" research; Ecological studies |
|
| 3a |
SR of case-control studies |
SR of Level 3b and better studies |
| 3b |
Individual Case-Control Study |
Non-consecutive study; or one without consistently applied reference standards |
| 4 |
Case-series (and poor-quality cohort and case-control studies) |
Case-control study, poor or nonindependent reference standard |
| 5 |
Expert opinion without explicit critical appraisal, or based on physiology, bench research or 'first principles' |
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Note: †† Met when all patients died before the Rx became available, but some now survive on it; or when some patients died before the Rx became available, but none now die on it. The table is adapted and published with permission from the Oxford Centre for Evidence-based Medicine [11]. | ||
Ringdal et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine 2009 17:66 doi:10.1186/1757-7241-17-66 |
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