Systematic review


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Systematic review

  1. 1. Systematic review Prof. Aboubakr elnashar Benha university Hospital, Egypt
  2. 2. Outline I. What is systematic review II. Why to do systematic review III. When to do systematic review IV. Model of a Cochrane systematic review V. Steps to do a systematic review VI. Challenges of systematic reviews
  3. 3. I. What is a systematic review? A review of a clearly formulated question that uses systematic and explicit methods to 1. identify, select and critically appraise relevant research 2. collect and analyse data from the studies that are included in the review (Cochrane Reviewers’ Handbook 4.1.5)
  4. 4. Systematic review Meta-analysis Literature review Meta-Analysis The use of statistical techniques in a systematic review to integrate the results of included studies.
  5. 5. QUESTION Broad Focused SOURCES/ Usually unspecified Comprehensive; SEARCH Possibly biased explicit SELECTION Unspecified; biased? Criterion-based; uniformly applied APPRAISAL Variable Rigorous SYNTHESIS Usually qualitative Quantitative INFERENCE Sometimes Evidence-based evidence-based NARRATIVE SYSTEMATIC Cook, D. J. et. al. Ann Intern Med 1997;126:376-380
  6. 6. Level of evidence • I–1 Systematic reviews. I–2 One or more large double- blind RCT. • II–1 One or more well- conducted cohort studies. II–2 One or more well- conducted case-control studies. II–3 uncontrolled experiment. • III Expert opinion. • IV Personal experience
  7. 7. Why on the Top • Rigorous methodology • Peer reviewed • Relatively large sample size • Ensures the highest quality evidence
  8. 8. II. Why do we need it? • Too much trials 25000 biomedical journals in print 8000 articles published per day • All studies not equally well designed or interpreted So, we need a study of studies • To summarize evidence from studies that address a specific clinical question. • To explain differences among studies on the same question • To limit bias (rigorous methodology & clear reporting)
  9. 9. Example • Protocols in neurology units - 80% still recommend bed rest after LP • Systematic review of 10 trials of bed rest after spinal puncture – no change in headache with bed rest – Increase in back pain Serpell M, BMJ 1998;316:1709–10
  10. 10. • Many single trials had relatively low power • Avoid Type II error: Investigators did not detect a difference when a difference actually exists • This is not surprising as the power to detect a difference will have been increased by the increase in the sample size • Systematic reviews help us to avoid the personal bias inherent in traditional reviews and expert opinion • Results from systematic reviews are the cornerstone for developing practice guidelines
  11. 11. III. When can you do meta- analysis? • When more than one study has estimated an effect • When there are no differences in the study characteristics that are likely to substantially affect outcome • When the outcome and treatment effect have been measured in similar ways • When the data are available
  12. 12. When not to do a meta-analysis? • ‘garbage in – garbage out’ – a meta-analysis is only as good as the studies in it – meta-analysis in presence of serious publication and/or reporting biases may produce an inappropriate summary
  13. 13. IV. Model of a Cochrane systematic review
  14. 14. Cochrane: Prof. Archie Cochrane CBE, FRCP, FFCM (1909-1988) 1960-74: Director, MRC Epidemiology Research Unit 1972: Publication by Nuffield Provincial Hospital Trust of his book “Effectiveness and Efficiency : Random Reflections on Health Services” “It is surely a great criticism of our profession that we have not organised a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomised controlled trials.”
  15. 15. The Cochrane Collaboration • International collaboration • Prepares, maintains, and disseminates systematic reviews • Diverse internal structure (Review Groups, Centres, Fields, Methods Groups, the Consumer Network) Cochrane Library • The current resource with the highest methodological rigor • $235/year or abstracts only •
  16. 16. Cochrane Collaboration Collaborative Review Groups Fields The Consumer Network Centres Steering Group Methods Groups
  17. 17. The logo represents meta-analysis of 7 trials of IM corticosteroids given to mothers for foetal maturation in preterm infants [Chalmers et al].
  18. 18. Abstract Background Objectives Criteria for considering studies for this review Types of participants Types of intervention Types of outcome measures Types of studies Search strategy for identification of studies Methods of the review Description of the studies Methodological qualities of included studies Results Discussion Conclusions Implications for practice Implications for research Internal sources of support to the review External sources of support to the review Potential conflict of interest Acknowledgements Contribution of Reviewer(s) Synopsis Characteristics of included studies Table 01 results References to studies included in this review Additional references Typical Systematic Review “Skeleton”
  19. 19. V. Steps to do a systematic review • Well-Formulated Question • Efficient Search Strategies • Review Abstracts to Determine Eligibility • Apply Strict Inclusion/Exclusion Criteria • Extract the Data • Perform the Required Analyses (Meta- analysis) • Interpret the Results • Determine Implications for Health Care Policy and Practice
  20. 20. Methodology • At least 3 reviewers • Detailed description of : Trial design characteristics Why included / excluded Quality of included studies in details Source of articles • Electronic databases • Bibliography of selected articles • Hand searching Journals • “Gray” Literature • Key Informants • Web Searching
  21. 21. VI. Challenges for systematic reviews • Evidence into practice • Many interventions reviewed cannot be implemented in resource-poor situations • Most interventions reviewed so far don’t reflect developing world priorities • Very few studies that have been conducted in a developing country • Most developing country research that is found is excluded on quality grounds
  22. 22. Email:
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