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## PowerPoint Slideshow about 'How to Conduct a Meta-Analysis' - nhi

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Presentation Transcript

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

What is Meta-analysis?

- Synthesis of previous studies
- Providing a Summary estimate
- Steps
- Identify studies
- Define Eligibility Criteria
- Abstract Data
- Do Statistical Analysis

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

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

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

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

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...

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

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

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

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

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

Mantel Haenszel Method

- Download Spreasheet Calculator
- Strength of Mantel Haenszel
- Very powerful
- Widely Used
- Limitation
- Cannot Control For Confounding!

Peto’s Method

- Similar to Mantel Haenszel
- Download Calculator
- Simpler Computation
- No Control for Confounding
- Good for RCTs
- Requires 2 X 2 Table

Variance-Based Methods

- Download Calculators For:
- Rate Difference
- For only Relative Risk and 95% CI
- Strengths and Limitations
- Good For Rate Differences
- Computationally Intensive

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

Random Effects Model

- Download The Calculator!
- Strengths and Limitations:
- Can Generalize the Conclusions
- Computationally Intensive

Continuous Outcomes

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

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

Conclusion

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

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