Objective: In this paper, we have summarised the process of conducting SRs for underpinning clinical practice guidelines under the auspices of the European Association of Urology Guidelines Office.
Evidence acquisition: The process involves explicit methods and the findings should be reproducible. When conducting a SR, the essential first step is to formulate a clear and answerable research question. An extensive literature search lays the foundation for evidence synthesis. Data are extracted independently by two reviewers and any disagreements are resolved by discussion or arbitration by a third reviewer.
Evidence synthesis: In SRs, data for particular outcomes in individual randomised
controlled trials may be combined statistically in a meta-analysis to increase power when the studies are similar enough. Biases in studies included in a SR/MA can lead to either an over estimation or an under estimation of true intervention effect size, resulting in heterogeneity in outcome between studies. A number of different tools are available such as Cochrane Risk of Bias assessment tool for randomised controlled trials. In circumstances where there is too much heterogeneity, or when a review has included nonrandomised comparative studies, it is more appropriate to conduct a narrative synthesis. The GRADE tool for assessing quality of evidence strives to be a structured and transparent system, which can be applied to all evidence, regardless of quality. A SR not only identifies, evaluates, and summarises the best available evidence, but also the gaps to be targeted by future studies.
Conclusions: SRs and MAs are integral in developing sound clinical practice guidelines and recommendations.
Patient summary: Clinical practice guidelines should be evidence based, and systematic reviews and meta-analyses are essential in their production. We have discussed the key steps of conducting systematic reviews and meta-analyses in this paper.
Bibliographical noteThomas Knoll and Muhammad Imran Omar have contributed equally, and are recognised as Joint First Authors on the publication.
Figure 5 was created by the GRADE Working Group. We are grateful to Professor Holger Schünemann, from McMaster University, for allowing us to use this figure.
Funding/Support and role of the sponsor: None.
- systematic review