Systematic reviews: UKHSA Knowledge and Library 天美影院
Knowledge and Library 天美影院 (KLS) can provide support to conduct systematic reviews.
Evidence synthesis overview
Evidence synthesis is the process of bringing together information and knowledge from a variety of sources and disciplines to inform debates and decisions on specific issues. (as defined by the ).
The main types of evidence synthesis include:
- Systematic reviews聽
- Rapid reviews
- Mapping reviews
- Scoping reviews聽
- Umbrella reviews
Each follows explicit, systematic methods to collate and synthesise findings
of studies that address a clearly formulated question (as outlined in the .
The main stages of the evidence synthesis process are shown below:
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Initial scoping exercise
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Protocol development
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Literature searching
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Screening
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Data extraction
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Critical appraisal (optional in rapid mapping and scoping reviews)
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Synthesis of relevant evidence
Systematic or rapid systematic methodologies
Systematic review methodology
Systematic reviews are the gold standard in evidence synthesis. Systematic review methodologies involve:
- screening, data extraction, critical appraisal and synthesis are performed independently by 2 reviewers (鈥榠n duplicate鈥�), with any discrepancies resolved through discussion, or with a third reviewer
- high rigour and reduced bias聽
- considerable time and resources (can take 1 to 2 years)
Rapid review methodology
Rapid reviews use modified systematic methods to accelerate the review process, while maintaining transparency and integrity. For example, rapid review methodologies may:
- search fewer databases or limited grey literature聽
- include only one study type, setting, population group or outcome聽
- perform limited screening in duplicate (for example, 10% to 20%)聽
- use shorter timeframes and limit analyses聽
- update a previous systematic review
Key characteristics of the different types of reviews
Systematic reviews
Both systematic methodologies and rapid systematic methodologies can be applied to systematic reviews, scoping reviews, mapping reviews or umbrella reviews.
Systematic reviews should have a specific review question and clearly defined eligibility criteria, usually using the PICO (population, intervention or exposure, comparator, outcome) framework. Study data is summarised using narrative text and tables. Systematic reviews sometimes include a meta- analysis, a statistical technique that provides an overall summary measure of effect.
Systematic reviews should follow the guidance. The PRISMA 2020 statement includes a 27-item checklist to support transparent and complete reporting. A should be included to show the progress of citations through the review.
Scoping reviews
Scoping reviews look at the current state of evidence on a broad topic. They give an overview of what research exists. Scoping reviews are similar to mapping reviews. The key difference is that mapping reviews focus on a specific research question, while scoping reviews explore a wider topic. Scoping reviews usually follow the PCC (Population, Concept, Context) framework instead of the PICO framework.
Scoping reviews are not designed to answer questions like 鈥榳hat works鈥�?鈥�. Their aim is to explore a topic, concept or issue to help shape future research or policy development. They do this by clarifying key concepts, definitions or methods.
Scoping reviews tend to be exploratory and may involve refining the process of searching, data extraction and analysis as the review progresses. They tend to have in-depth data extraction, and synthesis can include qualitative analysis, narrative synthesis and/or maps and tables.聽 The critical appraisal of included studies is optional.
The can be used for transparent and complete reporting of scoping reviews.
Mapping reviews
Mapping reviews are used to map out and categorise the literature and may be used for broad questions covering a range of interventions, outcomes, and/or populations. They are similar in process to a scoping review, but are based on a specific review question, rather than a topic, and tend to follow the PICO framework.
Mapping reviews are not designed to answer questions like 鈥榳hat works鈥�?鈥�. Instead, they show where evidence exists and where there are gaps. This is often presented visually as an evidence gap map. The aim is to inform research priorities, funding, and set a strategic agenda.
Unlike scoping reviews, mapping reviews should use a predefined framework of 鈥榗oding categories鈥� for the evidence gap map. Apart from the coding categories, data extraction tends to be more limited than for a scoping review. Critical appraisal of included studies is optional, although when conducted it can be represented on the map.
Umbrella review
An umbrella review, or 鈥榬eview of reviews鈥�, identifies multiple systematic reviews on related research questions and analyses their results across agreed outcomes. Umbrella reviews normally address a broad scope.
Meta-analysis may be performed to provide an overall summary measure of effect.
Umbrella reviews can only capture evidence that has already been examined in an existing systematic review, so any new evidence would not be included. There are some limitations to these reviews, such as the comprehensiveness of available information provided about the included primary studies.
Assistance KLS provide for systematic and other types of reviews
It is essential that a member of KLS is involved in your review team as early as possible in order to discuss the methodology and process of conducting a review. Any type of systematic review needs to have a well-designed and comprehensive search strategy behind it 鈥� if you do not retrieve some of the relevant studies available, the review results will be limited and potentially biased.
Designing a good review takes time, including developing and testing search strategies, which can be an iterative process. Please to discuss, or see our literature search request page.
UKHSA staff are also able to commission a complete rapid review via one of our UKHSA evidence teams.聽Visit our page on rapid reviews for details.
Protocol
This describes the rationale and planned methods for your review. It should be written before your review begins and followed when you conduct the review. Guidance on writing a protocol is available in .
You should register your systematic review in the registry 鈥� this should be done before data extraction begins. For further guidance, check the following guide from BioMed Central (BMC): .
Literature searching
KLS can provide complex literature searches to help in the production of a systematic review. This involves:
- conducting preliminary scoping searches to find similar reviews (to reduce duplication of effort)聽
- developing the search strategy聽
- translating the strategy for other databases聽
- running the searches on a variety of sources聽
de-duplicating citations聽 - providing the results in Endnote or another suitable format聽
- citation or similar article searching can also be provided, using sources such as Web of Science, Scopus, PubMed and Google Scholar
Screening
We can advise you on the best way to screen your results and show you tools that can help this process.
Software tools
We offer training and guidance on using tools such as EndNote and EPPI-Reviewer.
Write-up
KLS can write up the methods for your review and help with production of the .
Examples of reviews
Examples of a systematic review:鈥�
- Hallmaier-Wacker L and others. . Arch Dis Child 2022: volume 107, issue 11, pages 988 to 994鈥�
- Chu D and others. . The Lancet 2020: volume 72, issue 4, pages 1500聽
- Wolfenden L and others. . Cochrane Database of Systematic Reviews 2022: volume 8, issue, pages CD011677
Examples of reviews
Examples of a rapid systematic review:鈥�
- Duval D and others. . BMJ 2022: volume 377, page e068743聽
- Noone C and others. . Cochrane Database Syst Rev 2020: volume 5, issue 5, page CD013632聽
- Rios P and others. . Syst Rev 2020: volume 9, issue 1, page 218
Examples of a scoping review:鈥�
- O鈥橳oole F and others. . Public Health England 2019鈥�
- Borschmann R and others. . The Lancet Public Health 2020: volume 5, issue 2, pages e114 to e126聽
- Belita E and others. . BMC Public Health, 2022: volume 22, issue 1, page 1244
Examples of a mapping review:鈥�
- Winters N and others. . BMJ Global Health 2019: volume 4, issue 4, page e001421聽
- Saran A and others. . Campbell Systematic Reviews 2020: volume 16, issue 1, page e1070
Examples of a rapid mapping review:
- Duval D and others. . Journal of Public Health 2024:鈥痸olume 47, issue 2, pages 268 to 302聽
- Bosworth M and others. . UK Health Security Agency 2022, UKHSA Evidence Review collection page (天美影院) 2024
Examples of an umbrella review:
- Shah N and others.. BMC Public Health 2021: volume 21, issue 1, page 2118聽
- Shi X and others. . BMJ Medicine鈥�2022: volume 1, issue 1, page e000184聽
- Abu-Odah H and others. . Health Soc Care Community 2022: volume 30, issue 6, pages e3265 to e3276
Example of a rapid umbrella review:鈥�
- Hatzikiriakidis K and others. 聽. Palliat Med 2023: volume 37, issue 8, pages 1079 to 1099
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