Rapid reviews

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Reviews of increasing complexity, from narrative reviews to systematic reviews... with complexity comes an increase in time & resources needed
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  • Updated.jpg This entry is out of date, and will not be updated, September 2018



See also Evidence-based health care | Question scans | Horizon scans | Scoping reviews | Snowballing | Systematic narrative review methods

"...Rapid reviews are a form of “knowledge synthesis in which components of the systematic review process are simplified or omitted to produce information in a timely manner." Tricco et al, 2015

"...Rapid reviews are increasingly undertaken in health care to meet the demands of decision-makers and clinicians, who ultimately need timely evidence to inform their decisions. Under time and resource constraints, scoping reviews may be a suitable alternative to the traditional systematic review (though it depends on the research question)...limited budgets to fund systematic reviews, may also increase pressure to fund a rapid review...."
"...Rapid evidence reviews are a resource-efficient way to identify and summarise the general characteristics, issues, data and knowledge gaps surrounding a problem. They aim to be rigorous, transparent and explicit in method, but make concessions for the timeliness and utility of the output, and thus are not full systematic reviews of the literature or wider evidence..."Rand Corporation Paper, 2014

Rapid reviews (also rapid evidence reviews or rapid evidence assessments) are a kind of accelerated systematic review that can be viewed, according to Khangura S et al, 2014, as part of a continuum of methodologies in assessing evidence. In the rapid review, you find common elements such as expert searching and the use of extended search techniques such as locating the grey literature. Rapid reviews are undertaken as decision-makers examine urgent and emerging needs (i.e., policy or clinical urgency), new medical devices and policy. The rapid review is also central to evidence-based decision-making for public health policy experts and medical officials who must use the evidence to make decisions.

The rapid review is a research methodology that uses shorter timeframes than for other evidence-based summaries. It provides a timely and valid view of evidence but sacrifices rigour. As such, RRs are both review and assessment, and respond to urgent clinical and public health-related questions. They aim to provide robust analyses of easily-retrievable evidence in less than six weeks (sometimes four weeks), typically requiring fewer resources and funding. Due to their rapid nature, the grey literature might not always be sought and preference may be given to the more readily available research published and written in English (introducing bias). In terms of methodology, rapid reviews follow most of the same principles of the systematic review but within a shorter time frame and in less detail. Some concessions are made in terms of methodological rigour in the rapid review. That said, RRs have their place in the field, and have gained favour in Canada, the United States and UK within the educational, government and policy sectors. (See for example AHRQ Search for Research Summaries, Reviews and Reports.)

See also Polisena J, Garritty C, Umscheid CA, Kamel C, Samra K, Smith J, Vosilla A. Rapid Review Summit: an overview and initiation of a research agenda. Syst Rev. 2015 Sep 26;4(1):111.

Rapid reviews' value

According to the research, RRs are (re)appraisals of evidence that fall somewhere between health technology assessments (HTAs) or reports, and fully-developed systematic reviews of interventions. In that sense, they are similar to scoping studies and question scans in the educational sectors. The other value derived from the rapid review is to place the research in an order of rigour similar to systematic reviews but does it given shorter, urgent timelines, and often in two months or less. The prominence of evidence-based medicine and its principles around synthesizing the evidence have led some health organizations to develop rapid methods for accessing, appraising and synthesizing the evidence. Typically this is a slow, expensive process and is not undertaken for research issues that have been studied fully or where there is a lack of convincing evidence. In any case, rapid reviews may offer a suitable alternative to more systematic methods. One of the first steps is to find out what has been written and what is already known. Rigorous systematic review searching is needed for a range of academic and scientific disciplines. Health librarians and biomedical researchers should consider REA-type reviews to address the need to apply the evidence more quickly without the need to conduct a full systematic review.

Rapid 'cumulation' critical but there are challenges

If the review is to be delivered in a shorter time frame or a smaller budget it may seem inevitable that it will no longer be able to remain transparent, rigorous, exhaustive and comprehensive. Featherstone et al (2015) discuss some of the issues around the rigour of rapid reviews. Some questions are worth asking about the methods used to created a RR:

  • What are the implications of the shortcuts implied or taken in a RR, and can we measure the impact?
  • Rapid reviews are increasingly undertaken to meet the demands of decision makers, who need timely evidence to inform their decisions. Under such constraints the time required to undertake a traditional systematic review may be prohibitive. Limited budgets to fund systematic reviews, may also increase pressure to fund a rapid review.
  • If the review is to be delivered in a shorter time frame or a smaller budget it may seem inevitable that it will no longer be able to remain transparent, rigorous, exhaustive and comprehensive. What are the implications of any shortcuts that might be taken? Can we measure the impact of such shortcuts? Which methods might be adopted when undertaking a rapid review? What do commissioners want? What is the balance between working smarter and short changing the commissioners? How do you create a team that can work together more efficiently within a shorter timescale?
  • Which methods should be adopted when undertaking a rapid review?
  • What do funders such as CIHR want in a rapid review? What is rigorous?
  • What is the balance between working smarter and short changing the process?
  • How do you create a team that can work together more efficiently within a shorter timescale? These are a few of the questions that need to be answered in an era of expedited research reviews.

In a broader sense, rapid reviews are a result of the vast knowledge economy that has developed exponentially in recent decades. The number of publishing outlets and ease of publishing in the digital era is responsible for the information explosion in medicine. The sheer amount of evidence available, coupled with rapid growth of scholarly publishing and communication tools, make it difficult and time-consuming to cumulate all of the evidence on a topic. The problem of locating many separate and similar clinical studies has led to the creation of newer forms of knowledge management such as the rapid review. Despite the concerns expressed about its methodological shortcomings, the REA is widely-used in public policy and health technology assessment.


  1. Does your question seem to be of the type where qualitative methods and synthesis would work just as well? where several people are not required to work closely and iteratively with the sort of timescale only available to full systematic reviews?
  2. Is there a theoretical framework for structuring your evidence assessment? Any theory must be explicit and standardized (especially about interventions) to make predictions for specific implementations of interventions
  3. What is required are detailed descriptions of the context of any intervention (in a downloadable format, amenable to further processing), so that reviewers/end-users can make informed decisions as to relevance
  4. In an ideal world, end-users would be sufficiently literate that they could do the RRs themselves - or at least find their way around the literature. Some are, and workshops can 'build capacity.' But who knows if your 'evidence culture' is sufficient enought? Many organizations do not have the resources to do more than simple evaluations.

Health librarians' role in RRs

Reviewing evidence takes time and health librarians can use various techniques to help their clients. One of the key questions for health librarians is how to assist researchers in the process of planning and carrying out research, and whether rapid assessments meet their needs. This requires a range of skills, knowledge and abilities on the part of the attending health librarian, and includes topics as diverse as understanding the challenges of information retrieval in a fragmented literature and the trends associated with finding the grey literature.

See CADTH's suggested timelines for rapid reviews

Components of a rapid review

To enhance the transparency of a rapid review, documents can be designed and used to guide the process, such as:

  • explicit and documented search strategies
  • assessment protocols (design statements outlining key criteria for review)
  • regular, periodic assessments during and after the fact

Search strategies must be documented and used to guide searching in order to:

  • access research using web-based search tools and databases, informed by a range and combination of search terms
  • pursue particular sources suggested by librarians and colleagues
  • respond to requests to locate grey literature, unpublished or less widely-circulated papers and reports

Search strategies identify the range of search approaches, terms and resources that were used. Searching generates a list of potentially relevant sources, from which researchers are able to focus on their own ideas and questions.

Other elements of a rapid review

Usually a review of the academic, grey and practitioner literature includes the following five steps:

  1. Design and conceptual clarification of rapid review
  2. Purposeful evidence-based searching, and gathering of evidence
  3. Assessment of what is known about policy
  4. A critical appraisal of existing research which is "time-limited" (for relevance; then full assessment)
  5. Validation and discussion among experts
  6. Preparation of interim assessment, and final report

In addition, search the online and print literature as comprehensively as possible and do the following;

  1. Collate descriptive outlines of the available evidence
  2. Critically appraise evidence (including an economic appraisal)
  3. Sift out studies of poor quality
  4. Provide overview of what the evidence is saying
  5. Quantities of literature and overall quality/direction of literature (Davies, 2003, p.18-19)

Key websites

Major review types

See CADTH's suggested timelines for rapid reviews

Literature review

  • Narrative, selective review (not systematic); collates relevant studies and draw conclusions from them
  • Time required to complete: 1 week to 2 months

Quick scoping review

  • Quick overview of research undertaken on a (constrained) topic (not systematic)
  • Time required to complete: 1-2 weeks to 2 months

Rapid review

  • Systematic search but a quick overview of existing research on a topic
  • Synthesis of evidence provided by these studies to answer the REA question
  • Time required to complete: 2 to 6 months (quicker than systematic review)

Full systematic review

  • Systematic. A broad review of existing research on a topic and synthesis of the evidence provided by these studies to answer the review question.
  • Time required to complete: 8 to 12 months minimum

Multi-arm systematic review

  • Systematic. Full map and synthesis of different types of evidence to answer the review question
  • Time required to complete: 12 months minimum

Review of reviews

  • Systematic. Same as any of the above methods but only includes reviews of other reviews
  • Time required to complete: Often quicker than other types of full systematic review


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