DUMC Library: Evaluating a SYSTEMATIC REVIEW article
Validity issues |
Size of treatment effect | Finding articles
Validity issues
Are the results valid?
- Did the review explicitly address a sensible question?
- Was the search for relevant studies detailed and exhaustive?
- Were the primary studies of high methodologic quality?
- Were the assessments of included studies reproducible?
What are the results?
- What are the overall results of the review?
- Were the results similar from study to study?
How can I apply the results to patient care?
- How can I best interpret the results to apply them to the care of patients in my practice?
- Were all patient important outcomes considered?
- Are the benefits worth the potential costs and risks?
Size of treatment effect
A systematic review is a concise summary of the best 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 of therapy:
| | Outcome
Yes | Outcome
No |
| Treated (Y) | a | b |
| Control (X) | c | d |
Risk of Outcome: Y = a/(a+b)
Risk of Outcome: X = c/(c+d)
- Absolute Risk Reduction (ARR) is the difference in risk between the control group (X)
and the treatment group (Y). ARR = X-Y
- Number Needed to Treat (NNT) is the number of patients that must be treated over a given period of
time to prevent one adverse outcome. NNT = 1/ARR
- Relative Risk (RR) is the risk of the outcome in the treated group (Y) compared to
the risk in the control group. RR = Y/X
- Relative Risk Reduction (RRR) is the percent reduction in risk in the treated group (Y)
compared to the control group (X). RRR = 1-RR x 100%
Finding articles of systematic reviews
PubMed:
- Use Clinical Queries for Systematic Review
Ovid:
- Search for systematic overview$.tw. or systematic review$.tw.
- Search for systematic.tw. and limit to review.pt. (publication type)
References:
- JAMA 1994 272:1367-1371
- ACP Journal Club 1996 May-June; A12-A13
From: Guyatt, G. Users' Guides to the Medical Literature: Essentials of Evidence-based Clinical Practice.
AMA Press, 2002 and Sackett, D.L. Evidence-Based Medicine. How to Practice and Teach EBM. Churchill-Livingstone,
2nd edition, 2001 (pocket cards).
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Last modified on: 16-Dec-04