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Searching for evidence: Levels of evidence

LKC Searching for evidence guide includes literature searching & reviews, evidence based practice resources and research support

Cochrane Qualitative and Implementation Methods

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Levels of evidence

Pyramid of Evidence (5S Model)

Evidence Pyramid

Source: EBM levels of evidence. EBM Pyramid and EBM Page Generator, 2006 [?] Trustees of Dartmouth College and Yale University. All Rights Reserved. Produced by Jan Glover, David Izzo, Karen Odato, and Lei Wang.

The Haynes 6S evidence model has an additional layer at the top of the pyramid for SYSTEMS (where evidence is integrated within clinical decision making systems).

Evidence pyramid with specific primary sources

Pyramid of evidence with primary sources

Image adapted from: Guide to Research Methods :The Evidence Pyramid, SUNY Downstate Medical Center. Viewed online 03/02/2020.

Deciding on the best types of study

Guide to study types to match clinical questions.

Type of question
Ideal type of study
Randomised control trial RCT
RCT | Cohort Study | Case Control
Prospective, blind controlled trial comparison to gold standard
Cohort study | Case Control | Case series or Case report
RCT | Cohort study | Case control
Cost analysis
Economic analysis
Meta-analysis, meta-synthesis & systematic reviews, when available, often provide best answers to clinical questions.
Source: From Australian EBP Librarians’ Institute Perth 2014 (Participant workbook)

Systematic review videos

CER Comparative effectiveness research

Comparative effectiveness research (CER) is the conduct and synthesis of research comparing the benefits and harms of different interventions and strategies to prevent, diagnose, treat and monitor health conditions in "real world" settings.

Source - Definition: NLM Resources for Informing Comparative Effectiveness. Viewed on 3/03/2020.

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NHMRC Levels of evidence

NHMRC Levels of Evidence

Table 1.3 Designation of levels of evidence: Levels of evidence Study design. Evidence obtained from:

I Systematic review of RCTs

II At least one RCT

III-1 Pseudorandomised controlled trials

III-2 Comparative studies with concurrent controls and allocation not randomised

III-3 Comparative studies with historical control or interrupted time series without a parallel control group

IV Case series, either post-test or pretest/post-test

Source: NHMRC (1999) How to Use the Evidence p.8. Viewed 23/07/2015

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