How to Conduct a Meta-Analysis

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
• Petos 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
Petos 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

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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...