LibGuides: Systematic Reviews: Types of Review

Types of reviews

There are many types of reviews published in literature.

They are characterised based on aims and objective of the review, how the information is gathered and how data is synthesised.

The type of study design/s to include in your review depends on what type of review best answers the research question. The question development framework and associated methodologies may also vary.

These two articles have classified the different types of reviews. The tables are extracted below.

Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J, 26(2), 91-108. https://doi.org/10.1111/j.1471-1842.2009.00848.x

Table 1 Main review types characterized by methods used (p94-5)

Label	Description	Search	Appraisal	Synthesis	Analysis
Critical Review	Aims to demonstrate writer has extensively researched literature and critically evaluated its quality. Goes beyond mere description to include degree of analysis and conceptual innovation. Typically results in hypothesis or model.	Seeks to identify most significant items in the field.	No formal quality assessment. Attempts to evaluate according to contribution.	Typically narrative, perhaps conceptual or chronological.	Significant component: seeks to identify conceptual contribution to embody existing or derive new theory
Literature review	Generic term: published materials that provide examination of recent or current literature. Can cover wide range of subjects at various levels of completeness and comprehensiveness. May include research findings.	May or may not include comprehensive searching.	May or may not include quality assessment	Typically narrative.	Analysis may be chronological, conceptual, thematic, etc.
Mapping review/ systematic map	Map out and categorize existing literature from which to commission further reviews and/or primary research by identifying gaps in research literature.	Completeness of searching determined by time/scope constraints.	No formal quality assessment.	May be graphical and tabular.	Characterizes quantity and quality of literature, perhaps by study design and other key features. May identify need for primary or secondary research.
Meta-analysis	Technique that statistically combines the results of quantitative studies to provide a more precise effect of the results.	Aims for exhaustive searching. May use funnel plot to assess completeness.	Quality assessment may determine inclusion/exclusion and/or sensitivity analyses.	Graphical and tabular with narrative commentary.	Numerical analysis of measures of effect assuming absence of heterogeneity.
Mixed studies review/mixed methods review	Refers to any combination of methods where one significant component is a literature review (usually systematic). Within a review context it refers to a combination of review approaches for example combining quantitative with qualitative research or outcome with process studies.	Requires either very sensitive search to retrieve all studies or separately conceived quantitative and qualitative strategies.	Requires either a generic appraisal instrument or separate appraisal processes with corresponding checklists	Typically both components will be presented as narrative and in tables. May also employ graphical means of integrating quantitative and qualitative studies.	Analysis may characterize both literatures and look for correlations between characteristics or use gap analysis to identify aspects absent in one literature but missing in the other.
Overview	Generic term: summary of the [medical] literature that attempts to survey the literature and describe its characteristics.	May or may not include comprehensive searching (depends whether systematic overview or not).	May or may not include quality assessment (depends whether systematic overview or not).	Synthesis depends on whether systematic or not. Typically narrative but may include tabular features.	Analysis may be chronological, conceptual, thematic, etc.
Qualitative systematic review/qualitative evidence synthesis	Method for integrating or comparing the findings from qualitative studies. It looks for ‘themes’ or ‘constructs’ that lie in or across individual qualitative studies.	May employ selective or purposive sampling.	Quality assessment typically used to mediate messages not for inclusion/exclusion	Qualitative, narrative synthesis.	Thematic analysis, may include conceptual models.
Rapid review	Assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research.	Completeness of searching determined by time constraints	Time-limited formal quality assessment	Typically narrative and tabular.	Quantities of literature and overall quality/direction of effect of literature.
Scoping review	Preliminary assessment of potential size and scope of available research literature. Aims to identify nature and extent of research evidence (usually including ongoing research).	Completeness of searching determined by time/scope constraints. May include research in progress.	No formal quality assessment.	Typically tabular with some narrative commentary.	Characterizes quantity and quality of literature, perhaps by study design and other key features. Attempts to specify a viable review.
State-of-the-art review	Tend to address more current matters in contrast to other combined retrospective and current approaches. May offer new perspectives on issue or point out area for further research.	Aims for comprehensive searching of current literature.	No formal quality assessment.	Typically narrative, may have tabular accompaniment.	Current state of knowledge and priorities for future investigation and research.
Systematic review	Seeks to systematically search for, appraise and synthesis research evidence, often adhering to guidelines on the conduct of a review	Aims for exhaustive, comprehensive searching	Quality assessment may determine inclusion/exclusion	Typically narrative with tabular accompaniment	What is known; recommendations for practice. What remains unknown; uncertainty around findings, recommendations for future research

Munn, Z., Stern, C., Aromataris, E., Lockwood, C., & Jordan, Z. (2018). What kind of systematic review should I conduct? A proposed typology and guidance for systematic reviewers in the medical and health sciences. BMC Medical Research Methodology, 18(1), 5. https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-017-0468-4

Table 1 Types of reviews

Review Type	Aim	Question Format	Question Example
Effectiveness	To evaluate the effectiveness of a certain treatment/practice in terms of its impact on outcomes	Population, Intervention, Comparator/s, Outcomes (PICO) [23]	What is the effectiveness of exercise for treating depression in adults compared to no treatment or a comparison treatment? [69]
Experiential (Qualitative)	To investigate the experience or meaningfulness of a particular phenomenon	Population, Phenomena of Interest, Context (PICo) [13]	What is the experience of undergoing high technology medical imaging (such as Magnetic Resonance Imaging) in adult patients in high income countries? [70]
Costs/Economic Evaluation	To determine the costs associated with a particular approach/treatment strategy, particularly in terms of cost effectiveness or benefit	Population, Intervention, Comparator/s, Outcomes, Context (PICOC) [14]	What is the cost effectiveness of self-monitoring of blood glucose in type 2 diabetes mellitus in high income countries? [71]
Prevalence and/or Incidence	To determine the prevalence and/or incidence of a certain condition	Condition, Context, Population (CoCoPop) [15]	What is the prevalence/incidence of claustrophobia and claustrophobic reactions in adult patients undergoing MRI? [72]
Diagnostic Test Accuracy	To determine how well a diagnostic test works in terms of its sensitivity and specificity for a particular diagnosis	Population, Index Test, Reference Test, Diagnosis of Interest (PIRD) [16]	What is the diagnostic test accuracy of nutritional tools (such as the Malnutrition Screening Tool) compared to the Patient Generated Subjective Global Assessment amongst patients with colorectal cancer to identify undernutrition? [73]
Etiology and/or Risk	To determine the association between particular exposures/risk factors and outcomes	Population, Exposure, Outcome (PEO) [17]	Are adults exposed to radon at risk for developing lung cancer? [74]
Expert opinion/policy	To review and synthesize current expert opinion, text or policy on a certain phenomena	Population, Intervention or Phenomena of Interest, Context (PICo) [18]	What are the policy strategies to reduce maternal mortality in pregnant and birthing women in Cambodia, Thailand, Malaysia and Sri Lanka? [75]
Psychometric	To evaluate the psychometric properties of a certain test, normally to determine how the reliability and validity of a particular test or assessment.	Construct of interest or the name of the measurement instrument(s), Population, Type of measurement instrument, Measurement properties [31, 32]	What is the reliability, validity, responsiveness and interpretability of methods (manual muscle testing, isokinetic dynamometry, hand held dynamometry) to assess muscle strength in adults? [76]
Prognostic	To determine the overall prognosis for a condition, the link between specific prognostic factors and an outcome and/or prognostic/prediction models and prognostic tests.	Population, Prognostic Factors (or models of interest), Outcome (PFO) [20, 34,35,36]	In adults with low back pain, what is the association between individual recovery expectations and disability outcomes? [77]
Methodology	To examine and investigate current research methods and potentially their impact on research quality.	Types of Studies, Types of Data, Types of Methods, Outcomes [39] (SDMO)	What is the effect of masked (blind) peer review for quantitative studies in terms of the study quality as reported in published reports? (question modified from Jefferson 2007) [40]