User's Guides to the Medical Literature
Evidence-Based Medicine Working Group
Are the Results Valid?
Did this review address a focused clinical question?
Were the criteria for article inclusion appropriate?
Is it unlikely that relevant studies were missed?
Was the validity of the included studies appraised?
Was the assessment of studies reproducible?
Were the results similar from study to study?
What Are the Results?
What are the overall results of the review?
How precise are the results?
Will the Results Help Me In My Patient Care?
Can the results be applied to my patients?
Were all clinically important outcomes considered?
Are the benefits worth the harms and costs?
JAMA 1994; 272:1367-1371
A Systematic Review is a concise summary of the Jest available evidence that addresses a sharply defined clinical question
A Meta-analysis is a systematic review that uses quantitative methods to summarize the results.
The test of homogeneity gauges whether it is reasonable to combine the results of individual studies; it asks if the differences in treatment effect from study to study are greater than one would expect as a result of chance alone.
For meta-analyses of therapy, the results are interpreted as in for articles on therapy:
|Outcome +||Outcome -|
Risk of Outcome
Treated (Y): Y = a/(a+b)
Control (X): X = c/(c+d)
Absolute Risk Reduction:
ARR = X - Y
Relative Risk or Risk Ratio:
Number Needed to Treat:
NNT = 1/ARR= 1/(X-Y)
Finding a Systematic Review
[see ACP J Club 1996 May-June; A12 - A13]