Systematic Reviews Class 4c


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Systematic Reviews Class 4c

  1. 1. systematic r e v i e w s Adam Dubrowski NUR 1022, Lecture 5
  2. 2. <ul><li>We will address the following 2 issues: </li></ul><ul><li>How is a systematic review different than a narrative review of the literature? </li></ul><ul><li>Advantages of the systematic review? </li></ul>Systematic Review
  3. 3. <ul><li>A systematic review is a literature review focused on a single question which tries to </li></ul><ul><ul><li>identify </li></ul></ul><ul><ul><li>appraise </li></ul></ul><ul><ul><li>select </li></ul></ul><ul><ul><li>synthesize </li></ul></ul><ul><li>all high quality research evidence relevant to that question. </li></ul>Systematic Review
  4. 4. <ul><li>Systematic reviews are regarded as the highest level of medical evidence by evidence-based medicine professionals . </li></ul><ul><li>An understanding of systematic reviews and how to implement them in practice is becoming mandatory for all professionals involved in the delivery of health care. </li></ul>Systematic Review
  5. 5. <ul><li>There are mechanisms to overcome bias in the review which involves following a rigorous methodology . </li></ul>Systematic Review
  6. 6. <ul><li>Formulate a Research Question </li></ul><ul><li>1.1 Specify the Population, Intervention or Exposure, Methodology, Outcome (close to PICO) </li></ul><ul><li>1.2 Specify inclusion and exclusion criteria (of literature) </li></ul><ul><li>1.3 Determine restrictions: Time frame, Unpublished data, Language </li></ul>The Process of Conducting a Systematic Review
  7. 7. <ul><li>Conduct Literature Search </li></ul><ul><li>2.1 Decide on information sources: </li></ul><ul><li>bibliographical databases </li></ul><ul><li>key journals </li></ul><ul><li>articles, funding agencies, pharmaceutical company registries etc. (document!) </li></ul><ul><li>2.2 Identify Titles and Abstracts </li></ul>The Process of Conducting a Systematic Review
  8. 8. <ul><li>Apply Inclusion and Exclusion Criteria </li></ul><ul><ul><li>Determine the minimum methodological standards that studies must meet </li></ul></ul><ul><li>3.1 Apply inclusion and exclusion criteria to titles and abstracts </li></ul><ul><li>3.2 Obtain full study reports for eligible titles and abstracts </li></ul><ul><li>3.3 Apply inclusion and exclusion criteria to full study reports </li></ul><ul><li>3.4 Select final eligible studies </li></ul><ul><li>Document! </li></ul>The Process of Conducting a Systematic Review
  9. 9. <ul><li>Abstract Data </li></ul><ul><li>4.1 Assess methodological quality of studies (validity assessment) </li></ul><ul><li>4.2 Abstract data from each study about participants, exposure or intervention, experimental design </li></ul><ul><li>4.3 Abstract results </li></ul>The Process of Conducting a Systematic Review
  10. 10. <ul><li>Conduct analysis </li></ul><ul><li>5.1 Explore heterogeneity </li></ul><ul><li>5.2 Determine methods for summarizing results </li></ul><ul><li>5.3 Combine results if appropriate </li></ul><ul><li>(i.e. meta-analysis) </li></ul>The Process of Conducting a Systematic Review
  11. 11. combining results
  12. 12. Meta-Analysis : statistical technique for quantitatively combining the results of multiple studies that measure the same outcomes into a single pooled summary estimate. Combining Results
  13. 13. Combining Results Study results are weighted by their sample size, which yields a weighted average. There is usually a statistical test of heterogeneity among study weighted means = is the between study variance greater than expected by chance?
  14. 14. Confidence Intervals: range between two values within which it is probably that the true value lies for the whole population of patients from which the study patients were selected. Differences Among Studies
  15. 15. <ul><li>Wide confidence intervals can results from a lack of precision resulting from inclusion of a small number of studies. </li></ul>How Precise Were the Results?
  16. 16. <ul><li>Wide confidence intervals can results from a lack of precision resulting from inclusion of a small number of studies. </li></ul>How Precise Were the Results?
  17. 17. <ul><li>The selective publication of manuscripts based on the magnitude, direction or statistical significance of the study results. </li></ul>Publication Bias
  18. 18. Success of Publication Bias Authors decide that reporting a negative study is worthless and uninteresting. Report completion Interim analysis shows that a study is likely to be negative, and the study is dropped. Study completion No registries were kept of approved trials –this has recently changed. Institution/ Ethics Review Board approval Proposal selectively cites positive studies. Trial design, organization, and funding Small studies, which are more likely to be negative less likely to be published. Preliminary and pilot studies Actions Contributing to Bias Phases of research publication
  19. 19. Applying the Results to Patient Care
  20. 20. <ul><li>Consider whether: </li></ul><ul><li>The population sample covered by the review could be different from your population in ways that would produce different results? </li></ul><ul><li>Your local setting differs from that of the review? </li></ul><ul><li>You can provide the same intervention in your setting? </li></ul>1. How Can I apply the Results to Patient Care
  21. 21. <ul><li>Consider outcomes from the point of view of the: </li></ul><ul><li>Individual </li></ul><ul><li>Policy makers and professionals </li></ul><ul><li>Family/careers </li></ul><ul><li>Wider community </li></ul><ul><li>Systematic reviews frequently do not report the adverse effects of treatment. </li></ul>2. Were all Patient-Important Outcomes Considered?
  22. 22. <ul><li>Consider: </li></ul><ul><li>Whether any benefit reported outweighs any harm and/or cost. If this information is not reported can it be filled in from elsewhere? </li></ul>3. Are the Benefits worth the Cost and Potential Risks?