Evidence-based Medicine Toolkit

LevelRx/prevention,aetiology/harm4 Case-series (andpoor qualitycohort andcase–controlstudies)Prognosis Diagnosis Economic analysisCase-series (andpoor quality cohortand case–controlstudies)Any of:• reference standard was notobjective, unblinded or notindependent;• positive and negative tests wereverified using separate referencestandards;• study was performed in anappropriate spectrum of patients5 Expert opinion without explicit critical appraisal, or based on physiology, benchresearch or ‘first principles’Grades of recommendation:A Level 1a to 1cB Level 2a to 3bC Level 4D Level 51Systematic review with homogeneity2Clinical practice guidelinesAnalysis with no sensitivity analysisExpert opinion without explicitcritical appraisal, or based oneconomic theoryThese pages have been adapted from the CEBM Levels of Evidence: http://www.cebm.net, originally created by Dave Sackett and Suzanne Fletcher and subsequentlyadapted by Chris Ball, Bob Philips, Brian Haynes, Sharon Straus, Martin Dawes andPaul Glasziou.You should consult the web site for further details on how to use the levels96 Evidence-based Medicine Toolkit