ABSTRACT
Systematic review and meta-analysis procedures make use of explicit methods to methodically
search and critically appraise and synthesize the medical care research literature.
The methods involve refining a clinical question, designing a search procedure to
find eligible studies, and determining the validity of the eligible studies. Independent
data extraction by two or more reviewers is preferred. Agreement between the reviewers
with respect to relevance and validity should be measured. Meta-analysis procedures
estimate an overall average effect from the individual study effects and determine
whether these effects appear to measure the same relationship (that is, the studies
are not heterogeneous). In the inverse variance method, which is most frequently applied,
the overall effect is a weighted average of the individual study effects, where each
weight is the inverse of the study variance. To evaluate a systematic review, first
determine whether it addresses a question that is relevant to the patients, treatments,
and outcomes that are usual in your clinical practice. Then assess the validity of
the systematic review, which is reflected by quality of the individual studies, the
rigor with which the systematic methods were applied, and the extent of heterogeneity.
If the results of the systematic review are valid, then is the effect important enough
to make a difference in your clinical practice? Applying the results to an individual
patient involves the absolute treatment effect or the number needed to treat, and
an awareness of the patient's specific level of risk and personal preferences.
KEYWORDS
Systematic review - meta-analysis - randomized controlled trials - risk difference
- number needed to treat
