This document provides an overview of meta-analysis in medical research. It defines meta-analysis as a statistical analysis that combines the results of several separate but similar studies to provide a quantitative summary of the overall effects. The key steps of conducting a meta-analysis are outlined, including framing the research question, developing an search strategy to identify relevant studies, screening study titles and abstracts, assessing study quality, extracting data, and using statistical methods to analyze and interpret the pooled data. Meta-analysis provides a powerful approach for synthesizing evidence across studies to help inform clinical practice and policy decisions.

1. META -ANALYSIS IN
MEDICAL RESEARCH
Shibila VK
Pharmacy practice
NIPER,Mohali
1

2. Information about Health Care Is
Everywhere !!!
 But how do you know if one health care
intervention works better than another ?
 Or if it will do more harm than good?
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3. Too Much Information !!!
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4. There are more than 23,000 medical journals and if
you want to keep up to date, you have to read about
90 journals, in full, every day
Try to remember how you write your review
articles?
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5. Narrative reviews
• Most people are highlighting what they like and
what fit their hypothesis
• There is no clearly specified methods of
identifying, selecting, and validating including
information
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6. What is a Systematic review?
• Uses explicit preplanned scientific methods to
identify, select, appraise & summarizes similar
but separate studies
All reviews
SR
SR with
MA
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7. Knowledge Translation: from Clinical
Research to Practice Decisions
Clinical trial Cochrane Professionals Application
Observational collaboration Societies of policy
Studies
Clinical
policy
(guidelines)
Evidence
synthesis
(SR)
Evidence-
based
healthcare
Knowledge translation 7

8. Who Is Using Systematic Reviews?
Decision Makers
• Individual doctors and researchers
• Patients and consumers
• Policy makers
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9. Steps of a Systematic Reviews
 Frame research question (PICO/PECO)
 Develop protocol
 Develop search strategy
 Run search strategy in at least two databases
 Retrieve and de-duplicate citations
 Develop system for screening titles/abstracts and full-texts
 Screen titles/abstracts
 Retrieve and screen full-texts
 Develop forms for assessing ‘risk of bias’ and extracting data
 Conduct qualitative synthesis( combine the studies)
 Conduct meta-analyses (if appropriate)
 Write report of systematic review
 Update systematic review
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10. Frame research question
(PICO/PECO)
Approximate answer to the right question
Vs
Exact answer to the wrong question
Which one is better????
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11. 11

12. 12

13. Major databases for RCTs and
observational studies:
 MEDLINE/PubMED
(www.ncbi.nlm.nih.gov/sites/entrez?)
 Cochrane Central Register of Controlled Trials
(CENTRAL)
 EMBASE (www.embase.com)
 SCOPUS
 CTRI
 CINAHL
 PsychINFO
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14. Clinical question:
For patients with choroidal neovascularization
associated with age related macular degeneration,
do intra vitreal injections of Lucentis when
compared with Avastin prevent vision loss?
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15. To develop simple search
strategy!!!
Break into concepts
P Individuals with choroidal neovascularization associated
with age-related macular degeneration
I Lucentis
C Avastin
O Change in visual acuity or visual field
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16. To develop simple search
strategy!!!
Boolean operators
AND, OR, NOT
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A
N
D
CNV OR
Choroidal
neovascula
risation
Lucentis OR
Avastin

17. 17

18. `
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19. 19

20. Example:
What is the risk of cardiac
arrest in patients taking
H2 receptor blockers
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21. Identify keywords
Cardiac arrest
H2 receptor blockers
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22. Keyword 1 : Cardiac arrest
Cardiac arrest
Heart attack
(MeSH, TW,TIAB,cardiac*)
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23. Key word 2: H2 receptor blocker
H2 receptor blocker
Ranitidine
Famotidine
Cimetidine
(MeSH, TW,TIAB)
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24. Screening of Articles:
1. Based on title
2. Based on Abstract
3. Based on full text
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25. Reporting guidelines
• PRISMA
(Preferred Reporting Items for Systematic review and
Meta-Analysis)2009 flow diagram.lnk
• MOOSE (Meta-analysis of Observational Studies in
Epidemiology)
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26. Data extraction
 Author
 Year
 Study design
 Population
 Male / females
 Sample size
 Diagnostic test
 Intervention
 Outcomes etc.
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27. Quality assessment:
1. New castle Ottawa scale NOS.pdf
( For observational studies)
2. Jadad scale (For RCTs)
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28. Publication bias:
 Publication bias is a term used when studies
with positive results have a higher likelihood of
being published
 Publication bias can be linked to favorable or
unfavorable treatment of research findings due
to investigators, editors, industry, commercial
interests, or peer reviewers
 A funnel plot–a scatter plot of component
studies
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29. 29

30. 30

31. Heterogeneity
 Any kind of variability among studies
 Clinical heterogeneity
Patients, study settings , quality,intervention,outcome
• Statistical heterogeneity
Results of individual trials are not consistent with each
other
( p value for cochrane Q statistics < 0.10
I2 statistic > 50 % )
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32. What is a Meta-Analysis?
 Meta-analysis is an optional component of a
systematic review
 “A statistical analysis which combines the results of
several independent studies considered by the
analyst to be ‘combinable”
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33. When to do meta-analysis
• More than one study has estimated a treatment effect or
association
• The differences in the study characteristics are unlikely to
affect the treatment effect
• The treatment effect have been measured and reported in
similar ways
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34. Analysis
Revman software
CMA
STATA
M.Excel
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35. 35
Author ,
Year Odds ratio
Confidence
interval
Effect estimate
Effect size

36. Interpretation of forest plot
 Often, we have 6 columns in a forest plot.
 Column 1: Studies IDs
 Column 2 and column 3: Intervention group n/N and
Control group n/N
 Column 4: Relative risk (fixed) 95% CI
 Column 5: Weight (%)
 Column 6: Relative risk (fixed) 95% CI
same as 4, just in numerical format.
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37. Interpretation of forest plot
 The p-value indicates the level of statistical
significance.
 If the diamond shape does not touch the line of no
effect, the difference found between the two groups
was statistically significant.
 In that case, the p-value is usually < 0.05.
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38. Forest plot
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39. Forest plot
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THANK YOU