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How to Conduct a Meta-Analysis

How to Conduct a Meta-Analysis. Arindam Basu MD MPH About the Author Required Browsing. Objectives. Following the course, you will be able to : Define Meta-analysis Select Studies for a Meta-analysis Identify different types of Models Calculate Summary Effects

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How to Conduct a Meta-Analysis

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  1. How to Conduct a Meta-Analysis Arindam Basu MD MPH About the Author Required Browsing

  2. Objectives Following the course, you will be able to: • Define Meta-analysis • Select Studies for a Meta-analysis • Identify different types of Models • Calculate Summary Effects • Interpret Results of a Meta-analysis

  3. What is Meta-analysis? • Synthesis of previous studies • Providing a Summary estimate • Steps • Identify studies • Define Eligibility Criteria • Abstract Data • Do Statistical Analysis

  4. Identify Studies: Overview • Steps: • Search Your Personal Files First • Search Electronic Databases • Review Reference Lists of Articles • Contact Experts and Researchers • Retrieve New Articles • Evaluate Quality of the Studies • Set Up Eligibility Criteria

  5. Searching Electronic Databases • First, Define a Search Strategy • Limitations of Databases • incomplete and imperfect queries • language problems • problems with fugitive literature • Publication Bias is important • What is publication bias • How to deal with publication bias

  6. Evaluating Study Quality • Define Study Quality Criteria Early • Set Up A Good Scoring System • Develop A Form for Assessment • Calculate Quality for each Study • Use this for Sensitivity Analysis • stratify studies according to quality

  7. Defining Eligibility of Studies Select Eligible Studies Based On: • Study Designs • Years of Publication • Language • Choice among multiple articles • Sample-size or follow-up issues • Similarity of Exposure and/or Rx • Completeness of information

  8. Abstract Data - Review! Steps: • Identify Relevant Articles • Sort out Eligible Articles • Set up a Form for Abstraction • Enter the Eligible Studies • Use this as your database Statistical Analysis is next...

  9. Statistical Analysis - Overview • Select An Estimate of Effect • Choose An Effects Measure • Select An Effects Model • For Each Model: • Calculate Summary Effect Size • Calculate Confidence Intervals • Calculate Q-statistic for Homogeneity • Perform Sensitivity Analysis

  10. Selecting Estimate of Effect • Choose Only One Estimate • For RCTS, choose the one with • Once randomized always randomized • For nonrandomized trials, choose: • estimate adjusted only for age • that, and for a known confounder • the “most adjusted” estimate • estimate presented in the abstract

  11. Choosing An Effect Measure • RCTs or Cohort Studies • Rate Difference between Treatment and Control Groups • Ratio of Disease Rates • Case Control Studies • Odds’ Ratio • Rate Ratio

  12. Selecting An Effects Model • Available Types: • Fixed Effects Model • Random Effects Model • Difference Between the Two • Special Cases: • When Outcomes are not binary • Methods to be Used for them

  13. Fixed Effects Model • Methods: • Mantel Haenszel Method • Peto’s Method • General Variance Based Methods • For Rate Difference • For Rate Ratios • When only RR and 95 CI given • Tests of Homogeneity • Calculation of Q Statistic

  14. Mantel Haenszel Method • Download Spreasheet Calculator • Strength of Mantel Haenszel • Very powerful • Widely Used • Limitation • Cannot Control For Confounding!

  15. Peto’s Method • Similar to Mantel Haenszel • Download Calculator • Simpler Computation • No Control for Confounding • Good for RCTs • Requires 2 X 2 Table

  16. Variance-Based Methods • Download Calculators For: • Rate Difference • For only Relative Risk and 95% CI • Strengths and Limitations • Good For Rate Differences • Computationally Intensive

  17. Tests of Homogeneity • Establish Null Hypothesis that Effect Sizes Are Equal in All of the Studies [FAIL TO REJECT NULL] • Tested By Using Q-statistic • Q-statistic is distributed as chi-square distribution with degree of freedom = n-1 where n = number of studies

  18. Random Effects Model • Download The Calculator! • Strengths and Limitations: • Can Generalize the Conclusions • Computationally Intensive

  19. Continuous Outcomes • Measurement Scale: Continuous • Outcome Measured in Same Scale • Download Spreadsheet Calculator! • Essentially Extension of ANOVA • Useful For Integrating Social Science Research Data

  20. Sensitivity and Publication Bias • Conduct Sensitivity Analysis • Stratify studies by their quality rating • Compare Fixed and Random Effects • Deal With Publication Bias • Construct A Funnel Plot

  21. Conclusion • Presentation of Meta-analysis or Literature Synthesis • Download The Graph Maker • More Resources...

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