Reviewing the literature.

Are there different approaches to undertaking a literature review? Literature reviews aim to answer focused questions to: inform professionals and patients of the best available evidence when making healthcare decisions; influence policy; and identify future research priorities. Although over 14 types of reviews have been identified, literature reviews can be broadly divided into narrative (descriptive) reviews, scoping reviews, rapid evidence assessments (rapid reviews) and systematic reviews. In terms of rigour, if viewed as a continuum, narrative and systematic reviews would be at opposing ends of the continuum with scoping and rapid reviews at the midpoint. Narrative reviews usually provide a summary of a small selection of studies in order to support empirical research, are often difficult to replicate and can be biased because the review may not be comprehensive. The systematic review is considered the ‘gold standard’ because they attempt to identify, appraise and synthesise all empirical evidence that meets specific inclusion criteria to answer a highly focused clinical question; consequently a comprehensive systematic search of a wide range of sources of evidence is undertaken. Systematic reviews usually adhere to clear guidance from established centres such as Centre for Reviews and Dissemination (CRD) based in the UK and the Public Health Agency of Canada. Scoping reviews include a comprehensive search strategy but unlike systematic reviews do not synthesise the evidence. Scoping reviews are often used to map the literature in a broad context prior to undertaking a more focused systematic review. Rapid evidence assessments are used to summarise and synthesise research findings within the constraints of time and resources, and differ from systematic review in relation to the extensiveness of the search strategies and methods used to undertake the analysis. However, the review should be as thorough as possible within the given constraints and undertaken in a systematic manner.