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Many health professionals, students and academics including health researchers will have grappled with the challenges of undertaking a review of the literature and choosing a suitable design or framework to structure the review. For many undergraduate and master’s healthcare students their final year dissertation involves undertaking a review of the literature as a way of assessing their understanding and ability to critique and apply research findings to practice. For PhD and Master’s by Research students, a rigorous summary of research is usually expected to identify the state of knowledge and gaps in the evidence related to their topic focus and to provide justification for the empirical work they subsequently undertake. From discussions with students and colleagues, there appears to be much confusion about review designs and in particular the use and perhaps misuse of the term ‘systematic review’. For example, some quantitatively focused researchers subscribe to a ‘Cochrane’ approach as the only method to undertake a ‘systematic review’, with other researchers having a more pragmatic view, recognising the different purposes of a review and ways of applying systematic methods to undertake a review of the literature. Traditionally, systematic reviews have included only quantitative, experimental studies, usually randomised controlled trials.1 More recently, systematic reviews of qualitative studies have emerged,2 and integrative reviews which include both quantitative and qualitative studies.3
In this article, we will build on a previous Research Made Simple article that outlined the key principles of undertaking a review of the literature in a structured and systemic way4 by further exploring review designs and their key features to assist you in choosing an appropriate design. A reference to an example of each review outlined will be provided.
What is the purpose of undertaking a review of the evidence?
The purpose of a review of healthcare literature is primarily to summarise the knowledge around a specific question or topic, or to make recommendations that can support health professionals and organisations make decisions about a specific intervention or care issue.5 In addition, reviews can highlight gaps in knowledge to guide future research. The most common approach to summarising, interpreting and making recommendations from synthesising the evidence in healthcare is a traditional systematic review of the literature to answer a specific clinical question. These reviews follow explicit, prespecified and reproducible methods in order to identify, evaluate and summarise the findings of all relevant individual studies.6 Systematic reviews are typically associated with evaluating interventions, and therefore where appropriate, combine the results of several empirical studies to give a more reliable estimate of an intervention’s effectiveness than a single study.6 However, over the past decade the range of approaches to reviewing the literature has expanded to reflect broader types of evidence/research designs and questions reflecting the increased complexity of healthcare. While this should be welcomed, this adds to the challenges in choosing the best review approach/design that meets the purpose of the review.
What approaches can be adopted to review the evidence?
In 2009, a typology of reviews was published, identifying 14 types of reviews7 to which realist and integrative reviews can now be added. Table 1 highlights some of the more common reviews of the literature undertaken in healthcare.
In summary, we have identified and described a variety of review designs and offered reasons for choosing a specific approach. Reviews are vital research methodology and help make sense of a body of research. They offer a succinct analysis which avoids the need for accessing individual research reports included in the review, increasingly vital for health professionals in light of the increasing vast amount of literature available. The field of reviews of the literature continues to change and while new approaches are emerging, ensuring methods are robust and remain paramount. This paper offers guidance to help direct choices when deciding on a review and provides an example of each approach.
Competing interests None declared.
Provenance and peer review Commissioned; internally peer reviewed.