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APPENDIX 1: NHMRC Evidence Hierarchy

NHMRC Evidence Hierarchy: designations of ‘levels of evidence’ according to type of research question88

Level Intervention Diagnostic accuracy Prognosis Aetiology Screening Intervention

I

A systematic review of level II studies

A systematic review of level II studies

A systematic review of level II studies

A systematic review of level II studies

A systematic review of level II studies

II

A randomised controlled trial

A study of test accuracy with:

  • an independent, blinded
  • comparison with a valid reference standard, among consecutive persons with a defined clinical presentation

A prospective cohort study

A prospective cohort study

A randomised controlled trial

III-1

A pseudorandomised controlled trial(i.e. alternate allocation or some other method)

A study of test accuracy with:

  • an independent, blinded comparison with a valid reference standard, among non-consecutive persons with
  • a defined clinical presentation

All or none

All or none

A pseudorandomised controlled trial (i.e. alternate allocation or some other method)

III-2

A comparative study with concurrent controls:

  • Non-randomised,
  • experimental trial
  • Cohort study
  • Case-control study
  • Interrupted time series with a control group

A comparison with reference standard that does not meet the criteria required for Level II and III-1 evidence

Analysis of prognostic factors amongst persons in a single arm of a randomised controlled trial

A retrospective cohort study

A comparative study with concurrent controls:

  • Non-randomised,
  • experimental trial
  • Cohort study
  • Case-control study

III-3

A comparative study without concurrent controls:

  • Historical control study
  • Two or more single arm
  • study
  • Interrupted time series without a parallel control group

Diagnostic case-control study

A retrospective cohort study

A case-control study

A comparative study without concurrent controls:

  • Historical control study
  • Two or more single arm study

IV

Case series with either post-test or pre-test/post-test outcomes

Study of diagnostic yield (no reference standard)

Case series, or cohort study of persons at different stages of disease

A cross-sectional study or case series

Case series