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SSC in Evidence Based Medicine - Evaluating the evidence
- 1. Guide to Evaluating the Evidence Paula Funnell p.a.funnell@qmul.ac.uk Senior Academic Liaison Librarian (Medicine and Dentistry)
- 2. Why? To weigh up how valid and useful the research will be
- 3. 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%
- 4. 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
- 5. Brainstorm What factors should you be bearing in mind when reading an article? Think about • the research described • how it is reported
- 7. How are the results presented? • • • • Number needed to treat (NNT) Odds Ratio Relative risk Mean difference
- 8. Odds and risk 10 horses running, you bet on 1 horse Odds of winning 1:9 You versus the rest Risk of winning 1:10 You versus all the runners
- 9. Forest plots less than 1 1 more than 1
- 10. Forest plots Line of no effect less than 1 1 more than 1
- 11. Forest plots Line of no effect less than 1 1 more than 1
- 12. Forest plots Line of no effect Best estimate less than 1 1 more than 1
- 13. Forest plots Line of no effect Confidence interval Best estimate less than 1 1 more than 1
- 14. Forest plots Line of no effect Confidence interval Best estimate less than 1 1 more than 1
- 15. Forest plots Line of no effect Confidence interval Best estimate Pooled result less than 1 1 more than 1
- 16. 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
- 17. How it works • Involves answering a short questionnaire • We use the CASP questionnaires at http://www.sph.nhs.uk/what-we-do/publichealth-workforce/resources/critical-appraisalsskills-programme • The questionnaires were devised by doctors for doctors
- 18. Summary Validity Results Is it trustworthy? What does it say? Relevance Will it help?
- 19. Group critical appraisal 1) Did the review address a clearly-focused question?
- 20. Group critical appraisal 2) Did the authors look for the appropriate sort of papers?
- 21. Group critical appraisal Is it worth continuing?
- 22. Group critical appraisal 3) Do you think the important, relevant studies were included?
- 23. Group critical appraisal 4) Did the reviewers do enough to assess the quality of the included studies?
- 24. Group critical appraisal 5) If the results of the studies have been combined, was it reasonable to do so?
- 25. Group critical appraisal 6) What are the overall result of the reviews?
- 26. Group critical appraisal 7) How precise are these results?
- 27. Group critical appraisal 8) Can the results be applied to the local population?
- 28. Group critical appraisal 9) Were all important outcomes considered?
- 29. Group critical appraisal 10) Are the benefits worth the harms and costs?