Transcript Conducting Meta-Analysis in Health Research

CONDUCTING
META-ANALYSES IN
HEALTH RESEARCH
Kirsten Fiest,
PhD
June 23, 2015
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META-ANALYSIS
 A statistical method of combining data from multiple
independent sources
 Powerful tool to compare the effects of interventions,
determine the magnitude of association, or
prevalence/incidence of disease
 Often informed by the results of a systematic review
 Can assess differences between subgroups that may
not be possible in individual studies
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STATISTICAL PROGRAMS
 SAS, STATA, SPSS, R, spreadsheets, RevMan
 Graphics quality will differ
 Easiest to start with data in a spreadsheet
 Will need, at minimum, study identifier, effect size,
and measure of error
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ANALY TICAL METHODS
 Fixed effect
 Assumes there is one true effect size to be estimated
 Pooled estimate is the common effect size
 Weighting is based entirely on the size of the study
 Only source of error is within studies
 Random effects
 Allows the true effect to vary from study to study
 Trying to estimate the mean of a distribution of true
effects
 Weights assigned are more balanced
 Can be error within and between studies
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INTERPRETING META -ANALY TIC OUTPUT
Random-Effects Model (k = 11; tau^2 estimator: REML)
I^2 (total heterogeneity / total variability):
99.69%
Test for Heterogeneity:
Q(df = 10) = 3990.9717, p-val < .0001
Model Results:
estimate
-3.0934
se
0.9093
zval
-3.4018
pval
0.0007
ci.lb
-4.8757
ci.ub
-1.3111
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INTERPRETING A FOREST PLOT
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HETEROGENEIT Y
 Clinical and statistical heterogeneity should be
assessed
 Clinical heterogeneity
 Factors known to influence the relationship under
consideration
 Eg. disease duration, age, sex
 Statistical heterogeneity
 Measured most commonly by the I 2 and Q statistics
 Assesses whether any observed differences may be due to
chance alone
 Interpret with caution (power)
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STRATIFICATION
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PUBLICATION BIAS
 Potential bias for journals
to publish large studies
with significant results
 Statistical tests to
determine its presence
 Funnel plots
 Examine visually and
statistically
 Begg’s test is a rank
correlation method
 Egger’s test is a
regression-based method
 Trim and fill
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META-REGRESSION
 Used to identify trends across an extraneous variable
 Allows for the inclusion of continuous or categorical
variables
 Is the incidence of dementia changing over time?
 Does the prevalence of epilepsy differ by geographic
region?
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NETWORK META -ANALYSES
Method of
comparing
treatment effects
Pool data from
multiple studies with
one common arm
Can assess direct
and indirect effects
ACT, behavioural activation; CBT, cognitive-behavioural therapy; DYN,
psychodynamic therapy; IPT, interpersonal therapy; PLA, placebo; PST,
problem solving therapy; SST, social skills training; SUP, supportive
counselling; UC, usual care; WL, waitlist.
Barth et al., PLOS Med, 2013, 10(5) 11
REPORTING GUIDELINES
 PRISMA (Preferred Reporting Items for Systematic
Reviews and Meta-Analyses)
 MOOSE (Meta-Analysis of Observational Studies in
Epidemiology)
 Consider reporting guidelines for initial studies as
well (STARD, STROBE, CONSORT)
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Patten et al.; CJP, 2014, 59(11):60-614
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LIMITATIONS
 Limited by the reporting of individual papers
 Definitions, estimates provided, basic study details
 Quality of individuals studies may vary
 Heterogeneity between estimates may weaken some
conclusions
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RESOURCES
 Reporting guidelines
 Systematic Reviews in Health Care: Meta -Analyses in
Context, 2 nd Edition. Egger, Smith & Altman. 2008.
 Journals in your field of interest
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