www.library.qmul.ac.uk library services evaluating the evidence paula funnell [email protected]...
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www.library.qmul.ac.uk
LIBRARY SERVICES
Evaluating the evidence
Paula [email protected]
Senior Academic Liaison Librarian (Medicine and Dentistry)
www.library.qmul.ac.uk
i
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Why?
To weigh up how valid and useful the research will be
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Why? – to save time
• In order to keep up to date, clinicians would have to read 17 articles a day, 365 days a year
• Research is of variable quality
• Only an estimated 1% is judged clinically relevant
• Need to find the 1%
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Publication bias
Papers with “interesting” results are more likely to be:
• Submitted and accepted for publication
• Published in a major journal
• Published in English
• Quoted by authors
• Quoted in newspapers
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Brainstorm
What factors should you be bearing in mind when reading an article?
Think about
• the research described
• how it is reported
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Brainstorm
• the research described
• how it is reported
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RCT checklist
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How are the results presented?
• Number needed to treat (NNT)
• Odds Ratio
• Relative risk
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Odds and risk
Odds of winning
1:9
You versus the rest
Risk of winning
1:10
You versus all the runners
10 horses running, you bet on 1 horse
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Forest plots
more than 1less than 1 1
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Forest plots
more than 1less than 1 1
Line of no effect
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Forest plots
more than 1less than 1 1
Line of no effect
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Forest plots
more than 1less than 1 1
Line of no effect
Best estimate
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Forest plots
more than 1less than 1 1
Line of no effect
Best estimate
Confidence interval
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Forest plots
more than 1less than 1 1
Line of no effect
Best estimate
Confidence interval
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Forest plots
more than 1less than 1 1
Line of no effect
Best estimate
Confidence interval
Pooled result
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P-value
Could the result have occurred by chance?
p = 0.001 (1 in 1000)
p = 0.2 (1 in 5)
A p-value of less than 0.05 (1 in 20) is considered to be statistically significant
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How it works
• Involves answering a short questionnaire• We use the CASP questionnaires at
http://www.sph.nhs.uk/what-we-do/public-health-workforce/resources/critical-appraisals-skills-programme
• The questionnaires were devised by doctors for doctors
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Summary
Validity
Is it trustworthy?
Results
What does it say?
Relevance
Will it help?