Table 4.

Comparison of review types

	Systematic review *excluding qualitative systematic reviews	Scoping review	Overview of systematic reviews	Rapid review	Modular review
Description	Seeks to systematically search for, appraise and synthesise research evidence, adhering to guidelines on the conduct of a review [25]	Preliminary assessment of potential size, nature and scope of available research literature [12]	Bring together, appraise and synthesise evidence in areas where multiple systematic reviews already exist [26]	Search for and review evidence within limited timeframe and scope [27]	Combines systematic modular search process with stepwise synthesis and appraisal of the evidence to produce ‘best’ evidence synthesis. Focuses on broad condition or problem for which there are competing interventions
Expected timeframe	24 months or more [5]	0.5–20 months, mean length around 6 months [28]	6–18 months [3]	< 6 months [9]	6–18 months
Search	Comprehensive, systematic [25]	Broad [29]	Comprehensive, systematic [26]	Limited by time and resource constraints [27]	Comprehensive, systematic. Modular search allows searching on up to 50 modular variations.
Screening	Title-Abstract: Double independent screening recommended [30] Full text: Double independent screening [30, 31]	Title-Abstract: No established method but double independent screening recommended [14, 29] Full text: No established method but double independent screening recommended [29]	Title-Abstract: No established method but double independent screening recommended Full text: No established method but double independent screening recommended [3]	Title-Abstract: Often single screening, dual screen of at least 20% of abstracts recommended [9] Full text: Often single screening [9, 32]	Title-Abstract: Single screening with quality control measures Full text: Double independent screening
Data Extraction	Double independent extraction [33]	Double independent extraction recommended [14, 29]	Double independent extraction [34]	Single extraction, quality control measures recommended [9, 32]	Single extraction with quality control measures
Appraisal	Formal quality appraisal [35]	Formal quality appraisal often omitted [14, 36]	Formal quality assessment of included SRs; risk of bias of primary studies can be reported or independently assessed [37]	Formal quality appraisal often omitted [32] but recommended [9]	Relies primarily on existing quality assessment, quality assessment gaps filled as needed.
Synthesis	Uniform narrative and tabular synthesis on all data, often with meta-analysis [38]	Narrative and tabular without meta-analysis [14, 39]	Narrative and tabular synthesis, usually from systematic reviews [37]	Narrative and tabular [40]	Narrative and tabular synthesis on all data. Meta-analysis of data from “ES documents” where appropriate.