Review types

Description 

It combines the strength of a critical review with exhaustive search processes and strategies. A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. 

The overarching purpose of a systematic review is to identify, analyse, appraise, and arrive at a considered and balanced judgement. Individual sources of research are gathered and evaluated side-by-side. Reviewers will rigorously create a record of the origin of the information and data they find, summarise and appraise each piece of evidence according to a strict criteria, and synthesise findings based on the primary source material in their review. 

Common characteristics 

• Aim to identify, synthesise and present all of the scholarly research on a particular topic, including both published and unpublished studies. 
• An explicit, reproducible and uniformly applied criteria for the inclusion/exclusion of studies. 
• Conducted to reduce any bias, by accessing the validity of the findings of the included studies. 
• Time and resource intensive, often using a team or collaborative approach. 
• Contains a clear reason or motivation behind conducting a systematic review. 
• Can be many hundreds of pages long - depending on the topic area and focus of the review. 

Additional resources 

Example 

Pérez-Gaxiola, G., Cuello-García, C.A., Florez, I.D. and Pérez-Pico, V.M. (2018) ‘Smectite for acute infectious diarrhoea in children.’ Cochrane Database of Systematic Reviews, Issue 4: CD011526, pp. 1-57. [Online] [Accessed 6th August 2018] http://cochranelibrary-wiley.com/doi/10.1002/14651858.CD011526.pub2/full 

More information 

The Cochrane Collaboration. (2011) Cochrane Handbook for Systematic Reviews of Interventions. [Online] [Accessed on 6th August 2018] http://handbook-5-1.cochrane.org/chapter_2/box_2_3_b_timeline_for_a_cochrane_review.htm 

Description 

Sometimes when undertaking a literature review, you may be required to take a systematic approach. This approach may require you to use elements of a ’systematic review’, demonstrating that you have approached your review logically and with a set out plan. Some parts of this guide, therefore, may be useful, but others may not be required. 

A systematic literature search is often less rigorous in comparison to a full systematic review and less time intensive - usually completed within a couple of months. The scope is also usually much narrower and less evidence exhaustive than a systematic review where you would be expected to find all published and unpublished material. 

It is important to recognise the difference between a systematic review and a systematic literature review. The terms can often be used interchangeably. It is advisable to speak to the tutor that set the task if you are uncertain the level of detail you may require. 

Common characteristics 

• Set as part of an assignment or end of year dissertation or research project, usually taking between one and three months to complete. 
• Requires the use of multiple sources of information, such as multiple online databases, but there is some selectivity in the resources and databases used and excluded. 
• Does not often include grey or unpublished literature, drawing mainly on subscribed library resources. 
• Uses both qualitative, quantitative and mix methods primary research material. 
• Some limited justification for the inclusion and exclusion of search results, but not extensive. 
• Some basic recording of search results, usually in a table or series of tables, depending on databases searched. 
• Search results often form the basis of a narrative based discussion. 

Additional resources 

Example 

Han, J.S., Geminiani, E.T. and Micheli, L.J. (2018) ‘Epidemiology of Figure Skating Injuries: A Review of the Literature.’ Sports health, [Online] ‘Online First’ published 8th May 2018. [Accessed on 6th August 2018] DOI: 10.1177/1941738118774769 

More information 

Booth, A. P and Sutton, A. (2016) Systematic approaches to a successful literature review. 2nd ed., Los Angeles: Sage. 

Description 

Scoping reviews often precede a full systematic review. They aim to quickly identify key concepts underpinning the research area, as well as map out the primary sources of potential evidence and their availability. Scoping reviews tend to be conducted where there are few or no systematic reviews in existence in a particular research area, or where an research area is particularly complex or multi-disciplinary. 

Common characteristics 

• Used to identify whether or not a full review is justified by accessing the volume of literature and existing evidence base. 
• Helps to define the existing research domains, clusters, and pockets of evidence and existing knowledge. 
• Can be used to help develop or refine a review question, especially checking the breadth, depth and focus of a research question. 
• Helpful in identifying relevant keywords, concepts and terms, including any relevant synonyms. 
• Helpful in identifying the amount of time and resources required for a full review. 
• Useful in accessing and refining search techniques to capture relevant studies. 
• Detailed synthesis is not required. 
• Commonly undertaken as part of a funding application or before the protocol stage. 

Additional resources 

Example 

Tricco, A.C., Antony, J., Zarin, W., Strifler, L., Ghassemi, M., Ivory, J., Perrier, L., Hutton, B., Moher, D. and Straus, S.E. (2015) ‘A scoping review of rapid review methods.’ BMC Medicine, 13(1) pp. 224. 

More information 

Arksey, H. and  O’Malley, L. (2005). ‘Scoping studies: Towards a methodological framework.’ International Journal of Social Research Methodology: Theory & Practice, 8(1) pp. 19-32. 

Description 

Rapid evidence assessments or reviews allow for a structured and rigorous search, as well as a quality assessment of the uncovered evidence, but are not as extensive and exhaustive as a systematic review. They often provide a brief summary of the evidence discovered, so that informed, evidence-based, conclusions can be drawn. They tend to be used in making informed decisions often by policy makers or are used to justify the need for further research. 

Common characteristics 

• Applies systematic review methodology within short timeframe. 
• Provides a quick overview of the available evidence on a chosen topic 
• Acknowledges the inherent weaknesses of conducting a fast, rapid review, including bias. 
• Useful for finding evidence fast to support quick decisions making. 
• Purposely restricted to searching a limited number of key resources or databases 
• Limited in the types of studies they might include (e.g. randomised controlled trials) 
• Less focus on the overall quality of the original source material or evidence 
• Conducts only limited data extraction 
• Uses a smaller team over several weeks, catering for tight deadlines 

Additional resources 

Example 

Crawford, C., Boyd, C., Jain, S., Khorsan, R. and Jonas, W. (2015) ‘Rapid Evidence Assessment of the Literature (REAL©): Streamlining the systematic review process and creating utility for evidence-based health care.’ BMC Research Notes, 8(1) pp. 631-640. 

More information 

Department for International Development. (2015) Rapid Evidence Assessments. [Online] [Accessed on 6th August] https://www.gov.uk/government/collections/rapid-evidence-assessments

Description 

Maps out and categorises existing literature from which to commission further reviews and/or primary research by identifying gaps in the research literature. 

Common characteristics 

• Systematically and transparently collects and organises existing literature by categorising evidence. 
• Provides user friendly and easy to digest summaries, often in the form of a visual representation of the available data, such as a map. 
• Some reviews evaluate existing evidence, but do not attempt to synthesise the results and draw conclusions. 

Additional resources 

Example 

Gissing, S., Pradeilles, R., Osei-Kwasi, H., Cohen, E. and Holdsworth, M. (2017) ‘Drivers of dietary behaviours in women living in urban Africa: a systematic mapping review.’ Public Health Nutrition, 20(12) pp. 2104-2113. 

More information 

O’Leary, B.C., Woodcock, P., Kaiser, M.J. and Pullin, A.S. (2017) ‘Evidence maps and evidence gaps: evidence review mapping as a method for collating and appraising evidence reviews to inform research and policy.’ Environmental Evidence, 6(1) pp 1-9. 

Description 

A meta-analysis statistically combines results of quantitative studies to provide the precise effects of results. In a meta-analysis, the weight of the data extracted from the primary research material of each study is assigned a value based on mathematical criteria that is specified prior to the review. 

Common characteristics 

• Statistical techniques are used to combine the findings from primary quantitative research studies. 
• The new dataset is then objectively examined, leading to new insight. 
• Often conducted as part of a systematic review. 

Additional resources 

Example 

Dornelles, A., Artigalas, O., da Silva, A., Ardila, D., Alegra, T., Pereira, T., Vairo, F. and Schwartz, I. (2017) ‘Efficacy and safety of intravenous laronidase for mucopolysaccharidosis type I: A systematic review and meta-analysis.’ PLOS ONE, 12(8) p. e0184065. 

More information 

Borenstein, M. (2009) Introduction to meta-analysis. Chichester: Wiley.