Rapid Review

A rapid review is a form of evidence synthesis that uses simplified or abbreviated systematic review methods to produce findings within a shorter timeframe, typically weeks to a few months rather than the one to two years a full systematic review often takes. Rapid reviews are designed to provide timely evidence to inform urgent policy, clinical, or health system decisions when a full systematic review is not feasible within the required timeline.

Decision makers in healthcare, public health, and policy often face situations where evidence is needed quickly: during disease outbreaks, for urgent drug safety questions, or when policy windows are narrow. Waiting for a full systematic review may mean that decisions are made without any synthesized evidence at all. Rapid reviews fill this gap by providing a structured evidence summary that, while less comprehensive than a full systematic review, is more reliable than ad hoc literature searching or expert opinion alone. The COVID 19 pandemic dramatically increased the demand for rapid reviews and highlighted both their value and their limitations.

Rapid reviews accelerate the systematic review process by simplifying one or more methodological steps. Common shortcuts include searching fewer databases (sometimes only one or two major databases rather than the wider set a full systematic review would search), restricting the search to English language publications, limiting the date range, using a single reviewer for screening and data extraction (with a second reviewer checking a sample), simplifying or omitting quality assessment, and conducting a narrative synthesis instead of meta analysis.

The degree of abbreviation varies across rapid reviews, and there is no single standardized method. Some rapid reviews maintain most systematic review standards while reducing the search scope; others take more substantial shortcuts. The World Health Organization (a practical guide published in 2017) and the Cochrane Rapid Reviews Methods Group (interim guidance in 2020, updated in 2024 with 24 recommendations) have provided guidance on acceptable shortcuts and their implications for the reliability of the findings. Cochrane's 2020 interim guidance, for example, recommended limiting the main database search to CENTRAL, MEDLINE and Embase, limiting to English unless other languages are justified, dual screening at least 20% of abstracts before one reviewer screens the rest with a second reviewer checking all exclusions, and having a second reviewer verify single reviewer data extraction and risk of bias judgments.

The key tradeoff in rapid reviews is between speed and comprehensiveness. By searching fewer sources, rapid reviews may miss relevant studies, particularly those published in non English languages or in databases not searched. By using a single reviewer, they may miss eligible studies during screening or introduce extraction errors. By simplifying quality assessment, they may fail to identify important methodological limitations in included studies. Transparency about which shortcuts were taken and their potential impact on the findings is essential.

Rapid reviews should be clearly distinguished from systematic reviews in their reporting and should not be labeled as systematic reviews if they do not meet the full methodological standards. The label "rapid review" signals to readers that the evidence synthesis was conducted under time constraints with acknowledged methodological limitations.

Use a rapid review when an evidence based answer is needed within weeks to months and a full systematic review cannot be completed in time. Rapid reviews are appropriate for informing policy decisions during public health emergencies, responding to urgent clinical questions, and providing preliminary evidence summaries that can be updated with a full systematic review later. They are not appropriate when the evidence base is complex and extensive, when the question requires comprehensive identification of all relevant studies, or when the results will be used for regulatory decisions that demand the highest methodological rigor.

A common error is failing to document the methodological shortcuts taken and their potential impact on the completeness and reliability of the findings. Another mistake is presenting a rapid review as a systematic review, misleading readers about the level of rigor. Researchers sometimes use the rapid review format as an excuse to cut too many corners, producing a review that is neither rapid nor rigorous. Finally, failing to update a rapid review with a full systematic review when time allows means that decision makers continue to rely on a potentially incomplete evidence base.

During an emerging respiratory virus outbreak, a public health agency commissions a rapid review on the effectiveness of mask mandates for reducing viral transmission. The review team searches PubMed and Embase for English language publications from the past ten years, completes screening and data extraction in three weeks using two reviewers with one arbitrator, identifies 18 eligible studies, and conducts a narrative synthesis with a simplified quality assessment. The review is delivered six weeks after commissioning and finds low certainty evidence, mostly from observational studies, that mask mandates are associated with reduced transmission rates in community settings. The team recommends that a full systematic review be conducted as additional primary studies are published.