EBM - Evaluating a Systematic Review

MUSM Libraries: Evaluating a SYSTEMATIC REVIEW article

Appraise | Size of treatment effect | Finding articles

Appraise

What did they do? (Methods)
1. Did the review explicitly address a sensible question?
2. Was the search for relevant studies detailed and exhaustive?
3. Were the primary studies of high methodologic quality?
4. Were the assessments of included studies reproducible?
What was the answer? (Results)
1. What are the overall results of the review?
2. Were the results similar from study to study?
What did they say about the answer? (Conclusion)
1. Do the results of the study support the author/s conclusions?
2. Does the conclusion reflect the discussion?
3. Are there study limitations, and do these impact the conclusions?
4. Are potential discrepancies mentioned?
What do I do with this information?
1. How can I best interpret the results to apply them to the care of patients in my practice?
2. Were all patient important outcomes considered?
3. 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

Control Event Rate (CER)
The proportion of patients in the control group who experience the studied event.

Experimental Event Rate (EER)
The proportion of patients in the experimental treatment group who are observed to experience the outcome of interest.

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

Odds Ratio (OR)
The ratio of the odds of having the target disorder in the experimental group relative to the odds in favor of having the target disorder in the control group (in cohort studies or systematic reviews) or the odds in favor of being exposed in subjects with the target disorder divided by the odds in favor of being exposed in control subjects (without the target disorder).

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%

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Finding articles of systematic reviews

PubMed:

Select PubMed@Mercer and click on Clinical Queries, perform a search, then choose Systematic Reviews
Select PubMed@Mercer, select Customize under Article types, then select Systematic Reviews. Enter your search term/s.

Cochrane Library:

Select Cochrane Library, enter your search term/s. Select Cochrane Reviews or Other Reviews

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 Straus. Evidence-Based Medicine. How to Practice and Teach EBM. Churchill-Livingstone, 3rd edition, 2005 (pocket cards).

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Experimental group size:
Control group size:
Events in experimental group:
Events in control group:

EER
CER
ARR
RRR
NNT
OR/RR