MetaAnalysis: An Introduction

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Meta-Analysis An Introduction

• George A. Kelley, DA, FACSMSchool of Medicine,
• Dept. of Community Medicine,
• West Virginia University,
• Morgantown, WV
• Bio Funding Publications

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Interest and Excitement for Meta-Analysis

• Proliferation of information on health-related
  disease
• Need to try and make sense out of nonsense
• Enjoyment for combining and analyzing data

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Learning Objectives

• Identify what meta-analysis is
• Identify the advantages and different types of
  meta-analyses
• Identify the steps for conducting a meta-analysis
  of summary data

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Performance Objectives

• Define meta-analysis
• List and describe the advantages and types of
  meta-analyses
• List and describe the steps necessary for
  conducting a meta-analysis of summary data

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Major Topics Covered

• Overview of Meta-Analysis
• Steps for Conducting A Meta-Analysis

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I. Overview of Meta-Analysis

• Meta-Analysis Defined
• Advantages of Meta-Analysis
• Types of Meta-Analyses

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• Meta-Analysis Combining the results from many
  studies dealing with the same topic.

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B. Advantages of Meta-Analysis

• Study question specific narrow
• Data collection comprehensive specific
• Study selection based on uniformly applied
  criteria
• Data synthesis quantitative

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C. Types of Meta-Analyses

• 1. Summary Data
• 2. Individual Patient Data

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II. Steps for Conducting A Meta-Analysis

• Data Sources
• Study Selection
• Data Abstraction
• Statistical Analysis

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A. Data Sources

• Computer searches
• Cross-referencing
• Hand-searching
• Expert(s) to review list

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Data Sources-Example

• - Computer searches (Medline, Embase, Sport
  Discus, Current Contents, Dissertation Abstracts)
• - Cross-referencing from review and original
  articles
• - Experts to review list (Drs. James Hagberg
  Doug Seals)

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B. Study Selection

• Study designs
• Subjects
• Publication types
• Languages
• Interventions
• Time Frame

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Study Selection-Example

• - RCTs or CTs with a nonexercise control group
• - Progressive resistance training as the only
  mode of training
• - Females gt 18 years of age
• - Journal articles, dissertations, masters
  theses published in English

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Study Selection (cont.)

• Studies published indexed between January 1966
  and December 1998
• Bone mineral density assessed at femur, spine,
  and/or radius
• Training studies gt 16 weeks

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C. Data Abstraction

• Number of items coded
• Inter-coder bias
• Items coded

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Data Abstraction Example

• 242 possible items coded
• Data independently abstracted by first two
  authors
• Every data point reviewed for accuracy and
  consistency
• Major characteristics coded study, physical,
  exercise, primary secondary outcomes

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D. Statistical Analysis

• Choice of metric
• Choice of model/ heterogeneity
• Publication bias
• Study quality
• Moderator analysis

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1. Choice of Metric

• Original
• Standardized mean difference (Mean/Standard
  Deviation)

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2. Choice of Model/ Heterogeneity

• Fixed Effects
• Random Effects

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Metric, Model, Heterogeneity - Example
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3. Publication Bias

• Graphical methods
• Quantitative methods

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Funnel Plot - Example
r 0.50, p 0.007
Sample Size
Systolic ES (mmHg)
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4. Study Quality

• Difficult to assess
• Interpret with caution
• Numerous scales and checklists available

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5. Moderator Analysis

• Categorical Analysis
• Regression Analysis

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Categorical Analysis - Example
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Regression - Example
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