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REA Toolkit

• What is an REA?
• Planning an REA
• How to do an REA
• REA existing publications
• REA references

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REA Toolkit

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What is a Rapid Evidence Assessment?

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Rapid Evidence Assessment

Systematic. Quick overview of existing research on a (constrained) topic and a synthesis of the evidence provided by these studies to answer the REA question.
Time taken: 2 to 6 months

REAs provide a balanced assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research. They aim to be rigorous and explicit in method and thus systematic but make concessions to the breadth or depth of the process by limiting particular aspects of the systematic review process. 

The speed at which this is undertaken will depend on how quickly the evidence is needed, the available resource to carry out the REA and the extent to which reviewers are prepared to limit the systematic review process.

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How will it be rapid?

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There are a number of aspects of the systematic review process that can be limited in an REA to shorten the timescale. There is no requirement for all stages to be limited.

• The REA question - if the question is broad the search needs to be further limited.
• Searching – consider using less developed search strings rather than extensive search of all variants; if there are many existing recent reviews, then consider a review of reviews rather than of primary studies.
• Screening stage – REAs can use ‘grey’ and print sources but less exhaustively than systematic reviews. It is possible to only use electronically available abstracts and texts but this is unadvisable because of the increased risk of bias.
• Mapping stage - if included at all; often has to be limited in terms of the breadth of the initial evidence map.
• Data extract only on results and key data for simple quality assessment.
• Simple quality appraisal and/or synthesis of studies.

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When is it good to use an REA?

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Rapid Evidence Assessments can be undertaken in the following circumstances:

• When there is uncertainty about the effectiveness of a policy or service and there has been some previous research.
• When a policy decision is required within months and policy makers/researchers want to make decisions based on the best available evidence within that time.
• At policy development stage, when evidence of the likely effects of an intervention is required.
• When it is known that there is a wide range of research on a subject but questions still remain unanswered.
• When a map of evidence in a topic area is required to determine whether there is any existing evidence and to direct future research needs.
• As a starting point. Ideally, one is undertaken to answer a particularly pressing policy concern, and once the immediate question is answered it can form the basis of a more detailed full systematic review. In such cases, a Rapid Evidence Assessment could be better described as an ‘interim evidence assessment’.

In these situations an REA can provide a quick synthesis of the available evidence by shortening the traditional systematic review process.

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What are the disadvantages?

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In shortening the traditional systematic review process REAs risk introducing bias. Systematic reviews also suffer from biases but limiting the process increases the risk of them occurring. For example, limiting the search to published literature may introduce bias into the REA because of the exclusion of unpublished material. Therefore, the need for the evidence to be provided rapidly should outweigh the risk of increased bias. REAs (and all other review methods) should record how they have been less comprehensive than a full systematic review and discuss the likely levels of bias this has caused so that those taking decisions are aware of limitations of the evidence.

All review methods, including REAs, risk generating inconclusive findings that provide a weak answer to the original question. For example, there may not be studies of sufficient methodological quality to address the question. The tight timescales in an REA mean that if findings are inconclusive there is less time than in a systematic review to go back and reformulate the question or inclusion criteria.

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Methods for reviewing evidence index

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