Evidence-based Medicine Toolkit

94Levels of evidenceLevelRx/prevention,aetiology/harm1a SR 1 of RCTs SR of inceptioncohort studies; or avalidated CPG 21bIndividual RCT(with narrowConfidenceinterval)Prognosis Diagnosis Economic analysisIndividual inceptioncohort study with ≥80% follow up1c all or none All or none caseseries2aSR of cohortstudiesSR of eitherretrospective cohortstudies or untreatedcontrol groups inRCTsSR of Level 1 diagnostic studies; or aCPG validated on a test setIndependent blind comparisonof patients from an appropriatespectrum of patients, all of whomhave undergone both the diagnostictest and the reference standardAbsolute SpPins and SnNoutsSR of Level ≥2 diagnostic studiesSR of Level 1 economic studiesAnalysis comparing alternativeoutcomes against appropriatecost measurement, including asensitivity analysisClearly as good or better, butcheaper. Clearly as bad or worsebut more expensive. Clearly betteror worse at the same costSR of Level ≥2 economic studies