Implementing evidence into practice requires nurses to identify, critically appraise and synthesise research. This may require a comprehensive literature review: this article aims to outline the approaches and stages required and provides a working example of a published review.

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,1 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.1 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 question2; 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 UK2 and the Public Health Agency of Canada.3 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.2 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.2 However, the review should be as thorough as possible within the given constraints and undertaken in a systematic manner.

What stages are required to undertake a literature review?

The rationale for the review should be established; consider why the review is important and relevant to patient care/safety or service delivery. For example, Noble et al's4 review sought to understand and make recommendations for practice and research in relation to dialysis refusal and withdrawal in patients with end-stage renal disease, an area of care previously poorly described. If appropriate, highlight relevant policies and theoretical perspectives that might guide the review. Once the key issues related to the topic, including the challenges encountered in clinical practice, have been identified formulate a clear question, and/or develop an aim and specific objectives. The type of review undertaken is influenced by the purpose of the review and resources available. However, the stages or methods used to undertake a review are similar across approaches and include:

• Formulating clear inclusion and exclusion criteria, for example, patient groups, ages, conditions/treatments, sources of evidence/research designs;

• Justifying data bases and years searched, and whether strategies including hand searching of journals, conference proceedings and research not indexed in data bases (grey literature) will be undertaken;

• Developing search terms, the PICU (P: patient, problem or population; I: intervention; C: comparison; O: outcome) framework is a useful guide when developing search terms;

• Developing search skills (eg, understanding Boolean Operators, in particular the use of AND/OR) and knowledge of how data bases index topics (eg, MeSH headings). Working with a librarian experienced in undertaking health searches is invaluable when developing a search.

Once studies are selected, the quality of the research/evidence requires evaluation. Using a quality appraisal tool, such as the Critical Appraisal Skills Programme (CASP) tools,5 results in a structured approach to assessing the rigour of studies being reviewed.3 Approaches to data synthesis for quantitative studies may include a meta-analysis (statistical analysis of data from multiple studies of similar designs that have addressed the same question), or findings can be reported descriptively.6 Methods applicable for synthesising qualitative studies include meta-ethnography (themes and concepts from different studies are explored and brought together using approaches similar to qualitative data analysis methods), narrative summary, thematic analysis and content analysis.7 Table 1 outlines the stages undertaken for a published review that summarised research about parents’ experiences of living with a child with a long-term condition.8

In summary, the type of literature review depends on the review purpose. For the novice reviewer undertaking a review can be a daunting and complex process; by following the stages outlined and being systematic a robust review is achievable. The importance of literature reviews should not be underestimated—they help summarise and make sense of an increasingly vast body of research promoting best evidence-based practice.