A 4 part lecture series on the basics of Systematic Review and Meta-analysis, Part 2 discusses details of selection criteria and data extraction.

1. Basics of Systematic Review and
Meta-analysis
Part 2: Selection criteria and data extraction
Dr. S. A. Rizwan, M.D.,
Department of Community Medicine,
Velammal Medical College Hospital and Research Institute,
Madurai.

2. Selection criteria
• Necessary to make sure that the literature
used will be homogenous to the extent
possible
• To screen out a large body of irrelevant studies
• No one uniform criteria, depends on the study
question
• How to handle duplicate data or study

3. Example of selection criteria

4. Data extraction sheet
• Two authors needed
• First develop a pre-coded extraction sheet
together
• All relevant information from the study should
be extracted
• If certain info is not available in the full text or
abstract, contact the authors atleast twice

5. What info to extract
• Will depend on study question
• Basics
– study author, year of publication
– year of study
– sample size
– study design
– study population details
– outcome measure definition, exposure measure
definition
– effect size
– other comments

6. Example of data extraction sheet

7. Assumptions
• We cannot get data in the same manner in all
studies
• Therefore, we make certain assumptions to
carry the analysis forward
• Eg., Risk due to different forms of smokeless
tobacco use was considered to be equal

8. Effect size
• The main measure that we are going meta-
analyse
• Example
– Prevalence
– Odds ratio, relative risk
– Intervention effect
– Diagnostic test measures
– Others

9. Appraisal of individual study
• Use appropriate critical appraisal checklists
such as CASP, Cochrane risk of bias
assessment and others appropriate tools
• Classify studies into high or low quality, or
high or low risk of bias
• Will be used for sensitivity analysis

10. Example of critical appraisal

11. Example of critical appraisal

12. THANK YOU