Course Structure

Evidence Based Medicine, what is it?
What is Critical Appraisal?
How to find papers to answer your question?
How a paper is structured
Different forms of research
Different terminology used to describe research designs
Different categories of evidence
Hierarchy of evidence
Further terminology to be aware of
Statistical methods
Being Aware of Outcomes
Diagnostic studies
Terminology to be aware of in a diagnostic paper
Likelihood ratios and area under the curve
Critical Appraisal of a Diagnostic Study
Therapeutic studies
Treatment effect
Critical Appraisal of a Therapeutic Study
Final Quiz
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Likelihood ratios & area under the curve

Understanding likelihood ratios is part of the mastery of a diagnostic work up. Likelihood ratio help explain the significance of each test we perform and the difference they make to our patients.

The area under the curve is used during the development of a diagnostic test. The more accurate the test the better it separates those with the disease and those without it and the area under the curve can be used to quantify this.

This podcast covers

  • Positive and negative likelihood ratios
  • Fagan’s nomogram
  • Categorical Likelihood ratios
  • Area under the curve


Categories of likelihood ratios; Goodacre 2009 EMJ

Likelihood ratio Diagnostic value
1 None at all
0.5 Little clinical significance
2 to 5 Moderately increases likelihood of disease
5 to 10 Markedly increases likelihood of disease
0.1 to 0.2 Markedly decreases likelihood of disease
Over 10 Diagnostic
Less than 0.1 Rules out the disease


An example of a Fagan’s nomogram By Mikael Häggström [Public domain], via Wikimedia Commons


Significance of the area under a curve

Area under the curve Significance
.90-1 Excellent
.80-.90 Good
.70-.80 Fair
.60-.70 Poor
.50-.60 Fail


Once you’ve listened help consolidate the topics covered with the questions below.

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