Systematic Reviews: Common Types

90% of the time this is what people undertaking a 'Systematic Review' are actually doing. "A research team might conduct a scoping review to help develop, prioritize, and refine research priorities and inform future reviews or primary research. Scoping reviews are also often used to predict resource requirements (time and budget) to help define review protocols. Since scoping reviews are designed to determine the size and scope of literature available, quality assessment is not needed" (from 8 types of systematic reviews you should know, by Jennifer Baguss).

Purpose:

• To highlight the scope and size of a topic
• Aims to identify, characterise and summarise research evidence on a topic, Including identification of research gaps
• Useful for grant applications and newer research areas

Search:

• Can be ‘focused’ and date limited
• All types of studies are included
• Key databases are searched

(aka Rapid Evidence Assessment or Realist Review). "The rapid review is essentially a fast-tracked version of the systematic review. Rapid reviews are typically done when policymakers are working within a specific, tight timeframe and need quick turnaround. As a result, some critical systematic review steps are either modified or skipped entirely in a rapid review. For example, we might see less comprehensive search strategies, reduced use of grey literature (which can be challenging to find and process), more basic data extraction, and only simple quality appraisal" (from 8 types of systematic reviews you should know, by Jennifer Baguss).

Purpose:

• Assessment of what is already known about a policy or practice issue
• Often used for government / organisational reports or grant applications

Search:

• Can be very focused and limited
• Only key databases

(aka Meta-Review or Review of Reviews). "Umbrella reviews summarize data from multiple systematic reviews, rather than looking at primary studies. You can consider them to be a “review of reviews” or “overview of reviews.” Umbrella reviews are typically used when the researcher needs to address competing interventions in different reviews to report and highlight results. They typically include quality assessment of the studies within the reviews or of the reviews themselves and are often presented graphically or tabularly with some narrative aspects" (from 8 types of systematic reviews you should know, by Jennifer Baguss)..

Purpose:

• To synthesise results of multiple systematic reviews on a topic
• Useful for a research area that has already been heavily researched

Search:

• Limited to reviews but can use a search filter
• Can stick to key databases
• All searches can be date limited to 1990+

(aka Qualitative Evidence Synthesis, Systematic Thematic Synthesis). "A qualitative review looks at themes and concepts across individual qualitative studies. Qualitative reviews may also be known as “meta synthesis” or “qualitative evidence synthesis.” Qualitative reviews employ quality assessment, but unlike systematic reviews, where the assessment is done to determine inclusion or exclusion, quality assessment in a qualitative review is used to mediate messages. Naturally, this type of review uses a narrative approach to presenting results, but tables and diagrams are also often used" (from 8 types of systematic reviews you should know, by Jennifer Baguss).

Purpose:

• Searches, appraises and synthesises existing research evidence to ‘answer’ a specific research question
• Used to inform clinical decision-making and the creation of guidelines, alongside evidence from quantitative research

Search:

• Exhaustive

• Multiple databases and citation tracking (and probably grey literature)
• Limited to a qualitative studies
• Can only be limited by date with a rigorous justification, which must be related to the research question

Key points:

• Studies must be appraised for quality, but this is currently under debate

• Dual review

Timeline:

• 9-24 months

Example:

• Arai, L., Shaw, A., Feder, G., Howarth, E., MacMillan, H., Moore, T. H. M., Stanley, N., & Gregory, A. (2021, Jul). Hope, Agency, and the Lived Experience of Violence: A Qualitative Systematic Review of Children's Perspectives on Domestic Violence and Abuse. Trauma, Violence & Abuse, 22(3), 427-438. https://doi.org/10.1177/1524838019849582

(aka Integrative Literature Review)

Purpose:

• Allows for a comprehensive understanding of the literature concering a chosen topic through the appraisal, interpretation and synthesis of empiracal and theoretical literature

Search:

• Can have multi-faceted searches rather than a single version
• Multiple databases and grey literature
• Exhaustive search

Key points:

• Includes experimental and non-experimental studies (mixed method)
• Studies should be appraised (although many authors do not)
• Dual review
• Multi-step approach to synthesis
• Results are presented as themes and identified patterns

Timeline:

• 6-12 months

Example:

• Lobo, V., Fisher, A., Peachey, G., Ploeg, J., & Akhtar-Danesh, N. (2015). Integrative review: an evaluation of the methods used to explore the relationship between overtime and patient outcomes. Journal of Advanced Nursing, 71(5), 961-974. https://doi.org/https://doi.org/10.1111/jan.12560