ABSTRACT

Many hierarchies of quantitative evidence now rank systematic reviews of randomised controlled trials (RCTs) as the highest form of treatment outcome evidence, though traditional literature reviews are ranked near the bottom. To understand why systematic reviews are held in such high regard we need to understand how they differ from traditional literature reviews and the relationship between systematic reviews and meta-analysis, two terms that are sometimes mistakenly used as similes. Not all systematic reviews include a meta-analysis and not all meta-analyses are carried out in the context of a systematic review. Let us first consider what is a systematic review.