Meta-Analysis: An Introduction

1. Meta-Analysis: An Introduction George A. Kelley, DA, FACSMSchool of Medicine, Dept. of Community Medicine, West Virginia University, Morgantown, WV BioFundingPublications

2. 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

3. 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

4. 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

5. Major Topics Covered • Overview of Meta-Analysis • Steps for Conducting A Meta-Analysis

6. I. Overview of Meta-Analysis Meta-Analysis Defined Advantages of Meta-Analysis Types of Meta-Analyses

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

8. B. Advantages of Meta-Analysis • Study question specific & narrow • Data collection comprehensive & specific • Study selection based on uniformly applied criteria • Data synthesis quantitative

9. C. Types of Meta-Analyses 1. Summary Data 2. Individual Patient Data

10. II. Steps for Conducting A Meta-Analysis • Data Sources • Study Selection • Data Abstraction • Statistical Analysis

11. A. Data Sources • Computer searches • Cross-referencing • Hand-searching • Expert(s) to review list

12. 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)

13. B. Study Selection • Study designs • Subjects • Publication types • Languages • Interventions • Time Frame

14. Study Selection-Example - RCTs or CTs with a nonexercise control group - Progressive resistance training as the only mode of training - Females > 18 years of age - Journal articles, dissertations, & masters theses published in English

15. Study Selection (cont.) • Studies published & indexed between January 1966 and December 1998 • Bone mineral density assessed at femur, spine, and/or radius • Training studies > 16 weeks

16. C. Data Abstraction • Number of items coded • Inter-coder bias • Items coded

17. 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

18. D. Statistical Analysis • Choice of metric • Choice of model/ heterogeneity • Publication bias • Study quality • Moderator analysis

19. 1. Choice of Metric • Original • Standardized mean difference (Mean/Standard Deviation)

20. 2. Choice of Model/ Heterogeneity • Fixed Effects • Random Effects

21. Metric, Model, & Heterogeneity - Example

22. 3. Publication Bias • Graphical methods • Quantitative methods

23. Funnel Plot - Example r = 0.50, p = 0.007 Sample Size Systolic ES (mmHg)

24. 4. Study Quality • Difficult to assess • Interpret with caution • Numerous scales and checklists available

25. 5. Moderator Analysis • Categorical Analysis • Regression Analysis

26. Categorical Analysis- Example

27. Regression - Example

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