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Systematic Review

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  1. Systematic Review An Introduction

  2. Review • The general term for all attempts to synthesize the results and conclusions of two or more publications on a given topic. A review may or may not be systematic. R. Heshmat MD; PhD candidate

  3. Overview=Systematic Review • A review of the evidence on a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant primary research, and to extract and analyze data from the studies that are included in the review. R. Heshmat MD; PhD candidate

  4. Meta-analysis • When an systematic review incorporates a specific statistical strategy for assembling the results of several studies into a single estimate. R. Heshmat MD; PhD candidate

  5. A systematic review may, or may not, include meta-analysis. • Systematic review is always appropriate and desirable, but it may sometime inappropriate to statistically pool results from separate studies. R. Heshmat MD; PhD candidate

  6. A single study may produce a false negative results, due to inadequate sample size. • In the meta-analysis the necessary number of participants can be reached, and small effects can be detected or excluded with confidence. R. Heshmat MD; PhD candidate

  7. Systematic Review:Epidemiology of results Where the findings of an original study replace the individual as the unit of analysis.

  8. Narrative reviews • The classical review is subjective and therefore prone to bias and error. • Selective inclusion of studies that support the author’s view is common. • It ignores sample size, effect size, and research design. • Systematic reviews allow a more objectives appraisal. R. Heshmat MD; PhD candidate

  9. Historical notes • The statistical basis of meta-analysis reaches back to the 17th century in astronomy and geodesy. • In 1976 the psychologist Glass coined the term “meta-analysis”. • In the 1980s meta-analysis became increasingly popular in medicine. R. Heshmat MD; PhD candidate

  10. Finally: • Cochrane Collaboration was held in Oxford in October 1993. The Collaboration aims to help people make well-informed decision about health care by preparing, maintaining and promoting the accessibility of systematic review. R. Heshmat MD; PhD candidate

  11. Principles of and procedures for systematic review Systematic reviews should be as carefully planned as any other research project, with a detailed written protocol in advance.

  12. Stage 1 Planning the review Stage 2 Conducting a review Stage 3 Reporting & dissemination R. Heshmat MD; PhD candidate

  13. Stage 1 Planning the review Phase 0 Identification of the need for a review Phase 1 Preparation of a proposal for a review Phase 2 Development of a review protocol R. Heshmat MD; PhD candidate

  14. Stage 1 Planning the review Phase 0 Identification of the need for a review Phase 1 Preparation of a proposal for a review Phase 2 Development of a review protocol R. Heshmat MD; PhD candidate

  15. Stage 1 Planning the review Phase 0 Identification of the need for a review Phase 1 Preparation of a proposal for a review Phase 2 Development of a review protocol R. Heshmat MD; PhD candidate

  16. Stage 1 Planning the review Phase 0 Identification of the need for a review Phase 1 Preparation of a proposal for a review Phase 2 Development of a review protocol R. Heshmat MD; PhD candidate

  17. Stage 2 Conducting a review Phase 3 Identification of research Phase 4 Selection of studies Phase 5 Study quality assessment Phase 6 Data extraction and monitoring progress Phase 7 Data synthesis R. Heshmat MD; PhD candidate

  18. Stage 2 Conducting a review Phase 3 Identification of research Phase 4 Selection of studies Phase 5 Study quality assessment Phase 6 Data extraction and monitoring progress Phase 7 Data synthesis R. Heshmat MD; PhD candidate

  19. Stage 2 Conducting a review Phase 3 Identification of research Phase 4 Selection of studies Phase 5 Study quality assessment Phase 6 Data extraction and monitoring progress Phase 7 Data synthesis R. Heshmat MD; PhD candidate

  20. Stage 2 Conducting a review Phase 3 Identification of research Phase 4 Selection of studies Phase 5 Study quality assessment Phase 6 Data extraction and monitoring progress Phase 7 Data synthesis R. Heshmat MD; PhD candidate

  21. Stage 2 Conducting a review Phase 3 Identification of research Phase 4 Selection of studies Phase 5 Study quality assessment Phase 6 Data extraction and monitoring progress Phase 7 Data synthesis R. Heshmat MD; PhD candidate

  22. Stage 2 Conducting a review Phase 3 Identification of research Phase 4 Selection of studies Phase 5 Study quality assessment Phase 6 Data extraction and monitoring progress Phase 7 Data synthesis R. Heshmat MD; PhD candidate

  23. Stage 3 Reporting & dissemination Phase 8 The report and recommendations Phase 9 Getting evidence into practice R. Heshmat MD; PhD candidate

  24. Stage 3 Reporting & dissemination Phase 8 The report and recommendations Phase 9 Getting evidence into practice R. Heshmat MD; PhD candidate

  25. Stage 3 Reporting & dissemination Phase 8 The report and recommendations Phase 9 Getting evidence into practice R. Heshmat MD; PhD candidate

  26. Developing a Protocol for a Systematic Review

  27. Role of the protocol • A written document that forms the ’plan’ for the review • A protocol helps to avoid or minimise bias • Bias may occur in the retrieval, selection, extraction of data and evaluation of results • A protocol can (and should be) sent for external peer review R. Heshmat MD; PhD candidate

  28. Components of a protocol • Background • Review questions/ Objectives • Search strategy • Study selection criteria and procedures • Study quality assessment checklists and procedures R. Heshmat MD; PhD candidate

  29. Components of a protocol • Data extraction strategy • Data synthesis strategy • Project timetable R. Heshmat MD; PhD candidate

  30. Background section • Patients / disease characteristics • Course of disease • Pathophysiology • Interventions R. Heshmat MD; PhD candidate

  31. Research questions/ objectives • Population/ participants • Interventions • Outcomes • Study designs R. Heshmat MD; PhD candidate

  32. Literature search • Search strategy should specify which databases and other sources will be searched • Based on components of review questions • Do not need to present detailed search strategies in protocol R. Heshmat MD; PhD candidate

  33. Possible sources of literature • Electronic databases • Medline, Embase, PsycLIT, CINAHL • specialist trial registers e.g. CCTR • Handsearching • Checking reference lists • Personal communication • Pharmaceutical companies • Grey literature R. Heshmat MD; PhD candidate

  34. Study selection criteria • Should follow from research questions • i.e. population, interventions, outcomes, study design • Inclusion and exclusion criteria • Details of selection process should be set out here (how many reviewers, how are disagreements resolved?) R. Heshmat MD; PhD candidate

  35. Study quality assessment • Purpose of quality assessment? • For selection? For data synthesis? For implications of results? • Choose appropriate checklist (related to study design) • Details of assessment process (how many reviewers, disagreements etc) R. Heshmat MD; PhD candidate

  36. Data extraction strategy • Think about what data you need to extract from included studies to answer the questions • Pilot a draft data extraction form • Agree process (how many reviewers, disagreements etc) • Any manipulation of study data to be reported here R. Heshmat MD; PhD candidate

  37. Data synthesis • Will results be pooled? How? • How will differences between studies be taken into account? • Proposed sensitivity analyses? Subgroups? • How will results be displayed? • May not be possible to be specific at protocol stage R. Heshmat MD; PhD candidate

  38. Dissemination • How will you publish it? In what format? R. Heshmat MD; PhD candidate

  39. Timescale • Set out key milestones (e.g. searching, study selection, data extraction, draft report to peer review, final report) • Some stages may overlap • An end date for the review is the most important! R. Heshmat MD; PhD candidate

  40. Limitations of Systematic Review • Reporting bias and the inadequate quality of primary research are potentially serious problems for systematic reviews. • The quality of component studies is of crucial importance. • The dissemination of research findings is not a random process; rather it is strongly influenced by the nature and direction of results. R. Heshmat MD; PhD candidate

  41. Publication bias The publication or non-publication of research findings, depending on the nature and direction of the results Type of reporting bias R. Heshmat MD; PhD candidate

  42. Time lag bias The rapid or delayed publication of research finding, depending on the nature and direction of the results R. Heshmat MD; PhD candidate

  43. Multiple (duplicate) publication bias The multiple or singular publication of research finding, depending on the nature and direction of the results R. Heshmat MD; PhD candidate

  44. Citation bias The citation or non-citation of research finding, depending on the nature and direction of the results R. Heshmat MD; PhD candidate

  45. Language bias The publication of research finding in a particular language, depending on the nature and direction of the results R. Heshmat MD; PhD candidate

  46. Outcome reporting bias The selective reporting outcomes but not of others , depending on the nature and direction of the results R. Heshmat MD; PhD candidate

  47. The inclusion of data from unpublished studies can itself introduce bias. • Unpublished studies may be of lower methodological quality than published studies. R. Heshmat MD; PhD candidate