How to read a review paper.

Review papers commonly summarize the current knowledge on a selected topic. These types of papers are considered narrative reviews. Narrative reviews rarely detail the methods used to select the literature included, nor do the authors typically report the purpose of the review. Narrative reviews may be biased due to inadequate literature reviews or individual beliefs. A systematic review limits bias by disclosing the purpose of the paper, the assembly of the literature, and the appraisal of study quality. A meta-analysis, a specific style of systematic review, quantitatively pools data from individual studies for re-analysis. Pooling data increases the sample size and improves statistical power. The common representation of a meta-analysis is the forest plot. The forest plot demonstrates the odds ratio of individual studies, the weight each trial contributes to the analysis, and the 95% confidence intervals. Systematic reviews and meta-analyses are not without shortcomings, including issues related to study heterogeneity. Because of their transparency, systematic evaluations of the literature are superior to narrative reviews.