Systematic review and meta-analysis: tools for the information age.

The amount of available biomedical information is vast and growing. Natural limitations of the way clinicians and researchers approach this treasure trove of information comprise difficulties locating the information, and once located, cognitive biases may lead to inappropriate use of the information. Systematic reviews and meta-analyses represent important tools in the information age to improve knowledge and action. Systematic reviews represent a census approach to identifying literature to avoid non-response bias. They are a necessary prelude to producing combined quantitative summaries of associations or treatment effects. Meta-analysis comprises the arithmetical techniques for producing combined summaries from individual study reports. Careful, thoughtful and rigorous use of these tools is likely to enhance knowledge and action. Use of standard guidelines, such as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, or embedding these activities within collaborative groups such as the Cochrane Collaboration, are likely to lead to more useful systematic review and meta-analysis reporting.