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Grading studies lecture

Grading studies

arinbasu
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Grading studies lecture

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  1. From One Study to Many Studies How To Grad Evidence Arindam Basu Arindam.basu@canterbury.ac.nz

  2. Plan • Discuss different systems of grading evidence • Do an Example

  3. Objectives • Recap Steps of Evidence Based Health • Difference between Evidence and Quality • WhatGoes inQuality Appraisal • A Simple Class Exercise

  4. So Far, We Learned About Appraising One Study

  5. Lesson One: Evidence Appraisal is a Linear Systematic Process

  6. Review of Evidence-Based Practice • Step 1: Ask Questions • Step 2: Frame Questions in PICO Format • Step 3: Search and Retrieve • Step 4: Critically Appraise Literature • Step 5: Do Shared Decision Making or Decide

  7. Step 1: Ask Questions • These questions can be as broad based • Narrow Down the scope of Questions

  8. Step 2: Frame Question in PICO • Participants • Intervention or Exposure • Comparator or Comparison Groups • Outcomes that are being considered

  9. Step 3:Focused Literature Search • Construct Search Terms Using Boolean Logic • Use Multiple Databases • Precisely Define Search Terms • Narrow down or Broaden • Retrieve full text of the articles

  10. Step 4: Critically Appraise Literature • Is the Research Internally Valid? • Is the Research Externally Valid? • What is the Worth of this Information? • How does the Research Relates to Stakeholders?

  11. Is the Research Internally Valid? • What Kind of Study Is This? • Is the Study Adequately Powered? • What are the biases in the study? • How have the investigators Addressed Biases? • What kind of Confounding Variables?

  12. What Kind of Study is this? • Diagnostic or Screening Study • Study of Therapy or Harm • Epidemiological Observational Study on Prognosis • Retrospective Association Studies • Cross sectional Surveys • Other Types

  13. Biases = systematic errors • Selection Bias • Information Bias • How information collected from the participants from the study • Recall Bias • Biases need to be taken care of during the planning stages

  14. Effect of Confounding • Confounding Variables both the exposure or intervention and outcomes • Confounding can be controlled for at the initiation or planning stages of the study • Randomization • Matching • Multivariate Analyses

  15. Is the research Externally Valid? • Will the Results Apply to My Population? • Are the Results Generalizable?

  16. Worth of this evidence? • Results of the Study Lead to Cost Effective Solutions? • Do Patients, Payers, and Providers Accept? • Is the Study Repeatable?

  17. Lesson Two: Evidence Follows a Hierarchy Irrespective of the Problem

  18. Hierarchy of Evidence

  19. Lesson Three: Evidence is More than Internal Validity

  20. Where Evidence is Used • Critical Appraisal of an Individual Study • Developing Systematic Reviews • Framing Clinical Practice Guidelines • Framing Other Guidelines

  21. A Continuum Exists • Quality of An Individual Study (at one end) • Grading Strength of an Entire Body of Evidence (At the other end) SINGLE STUDY MANY STUDIES

  22. Revisiting PICO • P: “Different Strokes for Different Folks” • I: Same Problem can have Multiple Interventions • C: An Intervention can have Multiple Comparators • O: Systems Can Have Different Outcomes

  23. Types of Outcomes • Disease-Specific • Patient-Specific • System-Specific

  24. AHRQ Study 2002 • AHRQ in 1995-2000 studies found 19 effective systems • They identified seven domains across different study designs • Extensive Review of 1600 studies

  25. SORT (Taxonomy) • Strength Of Recommendation Taxonomy • Derived from the AHRQ Study of 2002 • Three Key elements: • 1. Quality: the extent to which identified studies minimize opportunity of bias (~= internal validity of the study) • 2. Quantity. - The number of studies that make up the grading, and the number of people who were included in these studies • 3. Consistency. -- the extent to which the study findings were similar across different studies on the same topic

  26. CEBM (See the Attached PDF)

  27. The US Preventive Services Task Force

  28. The Australian NHMRC Grading of Studies

  29. Guiding Principle • “Evaluating the strength of evidence is similar to distinguishing between causal and non-causal associations in epidemiologyConsistency and Strength of Association are highly important for causal vs non-causal association”

  30. “Grids” of Evidence Grading for RCT

  31. Grid for Systematic Review

  32. Grid for Observational Study

  33. Grid for Diagnostic Studies

  34. Class Exercise: • Appraise this article given out in the handout and assign a classification label based on • AHRQ Criteria for the appropriate Study • NHMRC • CEBM • We discuss this when we reconvene

  35. Afterword: Why Grading of Evidence Matters

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