MCC 2011 - Slide 24


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MCC 2011 - Slide 24

  1. 1. Systematic review and meta-analysis NNT NNH, setting up a protocol Theo Wiggers Cascais, February 16 th ,2011
  2. 2. <ul><li>We used for a Critical Appraisal of </li></ul><ul><li>the Literature: </li></ul><ul><li>“ two cohort studies, one prospective trial and one Cochrane study” </li></ul><ul><li>and we call it a systematic analysis </li></ul>
  3. 3. This lecture <ul><li>Systematic review and meta-analysis </li></ul><ul><li>Number needed to treat Number needed to harm </li></ul><ul><li>Making a protocol </li></ul>
  4. 4. The meaning of the name ? Professor Archibald Leman Cochrane (1909 - 1988) Director of the new Medical Research council’s Epidemiology Research Unit, Cardiff
  5. 5. <ul><li>Collaboration </li></ul><ul><li>Building on the enthusiasm of individuals </li></ul><ul><li>Avoiding duplication </li></ul><ul><li>Minimizing bias </li></ul><ul><li>Keeping up to date </li></ul><ul><li>Striving for relevance </li></ul><ul><li>Promoting access </li></ul><ul><li>Ensuring quality </li></ul><ul><li>Continuity </li></ul><ul><li>Enabling wide participation </li></ul>The Principles of The Cochrane Collaboration
  6. 6. Number of reviews
  7. 7. <ul><li>&quot;Every day someone, somewhere searches The Cochrane Library every second , reads an abstract every two seconds and downloads a full-text article every three seconds.&quot; - The Cochrane Library usage data 2009 </li></ul><ul><li>Impact Factor 2008: The Cochrane Database of Systematic Reviews has an Impact Factor OF 5.182 and is ranked 12th out of 107 in the ISI category Medicine, General & Internal </li></ul>The Cochrane Library
  8. 8. The Cochrane Library <ul><li>The Cochrane Database of Systematic Reviews ( CDSR ) contains the full text (including methods, results and conclusions) for Cochrane reviews and protocols. </li></ul><ul><li>The Database of Abstracts of Reviews of Effects ( DARE ), assembled and maintained by the Centre for Reviews and Dissemination in York, UK, contains critical assessments and structured abstracts of other systematic reviews, conforming to explicit quality criteria. </li></ul><ul><li>The Cochrane Central Register of Controlled Trials ( CENTRAL ) contains bibliographic information on hundreds of thousands of studies, including those published in conference proceedings and many other sources not currently listed in other bibliographic databases. </li></ul><ul><li>The Cochrane Methodology Register ( CMR ) contains bibliographic information on articles and books on the science of reviewing research, and a prospective register of methodological studies. </li></ul><ul><li>The Cochrane Collaboration section contains contact details and other information about CRGs and the other contributing groups within The Cochrane Collaboration. </li></ul>
  9. 9. 52 collaborative review groups Cochrane Colorectal Cancer Group
  10. 10. <ul><li>Colorectal, anal, and small bowel cancer </li></ul><ul><li>Benign proctological diseases, peritoneal diseases, and surgical treatment for inflammatory bowel diseases </li></ul><ul><li>Surgical anal diseases </li></ul><ul><li>Abdominal hernias </li></ul><ul><li>Appendiceal diseases </li></ul><ul><li>Diverticulitis </li></ul><ul><li>Peritonitis </li></ul>Cochrane Colorectal Cancer Group
  11. 11. <ul><li>Co-ordinating editor: Peer Wille-Jørgensen, Denmark </li></ul><ul><li>Deputy co-ordinating editor: Richard Nelson, USA </li></ul><ul><li>11 Editors 600 reviewers 150 External Peer Referees  </li></ul><ul><li>171 protocols and reviews </li></ul><ul><li>Neoplastic diseases of the small bowel 9 </li></ul><ul><li>Neoplastic diseases of the colon 57 </li></ul><ul><li>Neoplastic diseases of the rectum and anus 51 </li></ul>Cochrane Colorectal Cancer Group
  12. 12. <ul><li>Types of people (participants) </li></ul><ul><li>Types of comparison (intervention) </li></ul><ul><li>Types of outcome </li></ul>The three key components of a question for a systematic review Start with the preparation of a protocol followed by a review
  13. 13. <ul><li>Medline 30-80% of published RCTs </li></ul><ul><li>Embase </li></ul><ul><li>Cochrane Central Register Controlled Trials </li></ul><ul><li>Handsearching, conference proceedings </li></ul><ul><li>Other sources </li></ul>Search strategies
  14. 14. <ul><li>Cover sheet </li></ul><ul><li>Synopsis </li></ul><ul><li>Abstract </li></ul><ul><li>Text: introduction (background and objective), materials (selection criteria search strategy) and methods, results (description of studies, methodological quality , results), discussion, reviewers’ conclusions </li></ul><ul><li>Tables and figures </li></ul><ul><li>References </li></ul>Components a systematic review
  15. 15. <ul><li>Quality assessment of the study in order to limit bias: </li></ul><ul><li>selection bias (intervention vs control) </li></ul><ul><li>performance bias (exposure to intervention) </li></ul><ul><li>attrition bias (withdrawals during follow-up) </li></ul><ul><li>detection bias (outcome) </li></ul><ul><li>Rating validity A, B, C (unlikely, raises doubt, seriously weakens) </li></ul>What does allocation concealment mean?
  16. 16. <ul><li>Pooled analysis of enough qualified studies </li></ul><ul><li>RevMan </li></ul>When do we perform a meta-analysis ?
  17. 17. Forest plot
  18. 18. Forest plot
  19. 19. Do we always need a Randomized Controlled Trial? and a subsequent meta-analysis
  20. 20. Do we always need a Randomized Controlled Trial? Hazardous journeys Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials Gordon C S Smith, Jill P Pell BMJ VOLUME 327 20–27 DECEMBER 2003 Update 2006 next update to be expected?? We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute .
  21. 21. Do we always need a Randomized Controlled Trial? Prospective cohort studies preferable as part of a national audit program can bring strong and valid proof. For example in the Nordic audit report the same reduction of local recurrences after TME and 5x5 Gray are observed as in the Dutch and UK study
  22. 22. Number Needed to Treat <ul><li>NNT= absolute risk reduction :number of patients necessary to show a reduction of an event </li></ul><ul><li>Example: 5% less local recurrences </li></ul><ul><li>NNT= 20 </li></ul><ul><li>Relative risk reduction: percentage of reduction of risk </li></ul><ul><li>Example: reduction from 10-5%= 50% risk reduction </li></ul><ul><li>If from 1 to 0,5% </li></ul><ul><li>NNT 200 </li></ul><ul><li>Relative risk reduction= 50 % </li></ul>
  23. 23. Number Needed to Harm <ul><li>NNH= how many patients need to be exposed to a risk factor over a specific period to cause harm in one patient that would not otherwise have been harmed </li></ul><ul><li>Example </li></ul><ul><li>NNH=10 (if 100 individuals are exposed to the risk factor, 10 will develop the complication that would not have otherwise) </li></ul>Incidence of incontinence Radiotherapy 50% Surgery 40%
  24. 24. Making a protocol(1) <ul><li>Title </li></ul><ul><li>Background </li></ul><ul><li>Endpoint </li></ul><ul><ul><li>Primary endpoint </li></ul></ul><ul><ul><li>Secondary endpoint(s) </li></ul></ul><ul><li>Study design </li></ul><ul><li>Selection criteria </li></ul><ul><li>Criteria for inclusion </li></ul><ul><li>Criteria for exclusion </li></ul>
  25. 25. Making a protocol(2) <ul><li>Criteria for inclusion </li></ul><ul><li>Criteria for exclusion </li></ul><ul><li>Baseline screening </li></ul><ul><li>Stratification </li></ul><ul><li>Treatment arms </li></ul><ul><li>Statistical considerations </li></ul><ul><ul><li>Expected percentage in control arm </li></ul></ul><ul><ul><li>Improvement in experimental arm </li></ul></ul><ul><li>Planned sample size </li></ul>
  26. 26. Thank you for your attention