Flinders University Library
Search Smart

Evidence Based Medicine (EBM)

This guide is designed to walk you through the Evidence Based Medicine process: the elements of a well-formulated clinical question, types of studies, and the key critical appraisal questions that help determine the validity of evidence.

Different hierarchies of evidence

There are many different "levels of evidence" designed by health research institutions. The following are most appropriate for medicine:

JBI levels of evidence for interventional questions

 

 

JBI evidence hierarchy for intervention (therapy) questions


The NHMRC Levels of Evidence table with links to example articles in PubMed

Level

       Intervention

        Diagnosis

        Prognosis

NHMRC levels of evidence

I

   A systematic review of level II studies

   A systematic review of level II studies

   A systematic review of level II    studies

II

   Randomised controlled trial (RCT)

   A study of test accuracy with an independent, blinded comparison with a valid reference standard among consecutive persons with a defined clinical presentation

   Prospective cohort study

III-1

   Pseudo-RCT (alternate allocation or some other method was used rather than true randomisation

   As for level II, but a study that uses non-consecutive participants

 

III-2

   Comparative study with concurrent controls:

  A comparison with a reference standard that does not meet the criteria required for level II or/and III-1 evidence

  Analysis of the prognostic factors among the participants in one group of a RCT

III-3

  Comparative study without concurrent controls:

  Diagnostic case-control study

  Retrospective cohort study

IV

  Case series

  Study of diagnostic yield (no reference standard)

  Case series or  Cohort study where participants are at different stages of the disease/condition