www.library.qmul.ac.uk library services evaluating the evidence paula funnell p.a.funnell@qmul.ac.uk...

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LIBRARY SERVICES

Evaluating the evidence

Paula Funnellp.a.funnell@qmul.ac.uk

Senior Academic Liaison Librarian (Medicine and Dentistry)

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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?