Evidence Synthesis

National Collaborating Centre for Methods and Tools Rapid Review Guidebook

Timeframe/ Resources

~1-8 months. Time is divided between designing question/ search strategy, reviewing and evaluating sources, and summarizing. 

Usually multiple people to reduce bias, may include non-blinded appraisal and selection

Purpose/ Type of Question

Applies parts of Systematic Review methodology within a time-constrained setting; faster, but less rigorous as a result. Usually for a tightly defined question. Employs "shortcuts" (eg: limiting search terms) at the risk of introducing bias/ reducing comprehensivity. Useful for addressing issues needing quick decisions, such as developing policy recommendations.

Sources/ Searches

Sources are limited due to time constraints of searching, however still uses transparent and reproducible search methods. May exclude hand searching and grey lit, limited databases. May restrict by years, language, and other parameters to reduce results.

Inclusion/Exclusion & Appraisal

Should document steps/ decisions according to PRISMA, even if they are not followed (eg, risk of bias assessment). Still likely to have inclusion/ exclusion, critical appraisal, but may be constrained/ streamlined due to time constraints.

Synthesis/ Reporting

Descriptive summary of the findings. Can be qualitative, quantitative, or mixed. Tailored to the specific research question.

Limitations

Time and resource constraints limit generalizability and validity of findings 

Limiting search duration and limits introduces publication bias and other risks 

Methodology is not as agreed upon as other Reviews 

May only be one reviewer, increasing bias 

Search may not be comprehensive 

Possible non-blinded appraisal and selection 

Provide a limited interpretation of results

Summarized from: https://www.tandfonline.com/doi/full/10.1080/17489539.2017.1333683

Timeframe/ Resources

~1-3 months. Time is dived between designing question, effective search strategy, screening, critical appraisal of selected articles, discussion of findings.

Single person

Purpose/ Type of Question

ASubtype of rapid review. Provides a snapshot of the best available evidence on a focused question; typically identifies, critically appraises, and synthesizes evidence from 3 to 5 pieces of the best available evidence.

Sources/ Searches

Search may be comprehensive, but sources selected will be narrow. Decision making on search & selection needs to be documented and transparent.

Inclusion/Exclusion & Appraisal

STransparent inclusion/ exclusion criteria, ranking of different types of studies into different levels of evidence based on methodological rigor and appropriateness to the question. Studies deemed to represent the highest level of evidence (based on study design) and have most relevance to the question are retrieved for further analysis.

Synthesis/ Reporting

For each study: Is the study valid? What are the results? Will the results help locally? Authors should decide whether the evidence is weak or strong, if the study design and quality are good, and if the study findings are consistent. Recommendations may include implications for local context, need for updated studies, etc.

Limitations

Source selection can introduce high risk of bias

Not comprehensive/ representative of full body of knowledge on a subject