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Systematic Reviews

Glossary of terms

Glossary of Terms


An international organization for evidence synthesis, especially systematic reviews and meta‐analyses in relation to health (

Eligibility (Inclusion/Exclusion) Criteria

In systematic reviews, large numbers of search results get winnowed down to a comparatively small number of works that will be analyzed. The framing of the research question, and what the researchers deem relevant, constitute the criteria that works must meet to be eligible for comparison. Common criteria include: language, publication date, geography, characteristics of the population studied, intervention (or exposure), and study design.

Grey Literature

"Grey literature stands for manifold document types produced on all levels of government, academics, business, and industry in print and electronic formats that are protected by intellectual property rights, of sufficient quality to be collected and preserved by libraries and institutional repositories, but not controlled by commercial publishers, i.e. where publishing is not the primary activity of the producing body." (Schopfel, J. Towards a Prague definition of grey literature. Paper presented at the 12th Intl. Conference on Grey Literature, Prague, Dec. 6-7, 2010.)


"Medical Subject Headings: a thesaurus of medical terms used by many databases and libraries to index and classify medical information."(CEBM)


"Works consisting of studies using a quantitative method of combining the results of independent studies (usually drawn from the published literature) and synthesizing summaries and conclusions which may be used to evaluate therapeutic effectiveness, plan new studies, etc. It is often an overview of clinical trials. It is usually called a meta-analysis by the author or sponsoring body and should be differentiated from reviews of literature." (National Library of Medicine, MeSH Thesaurus)


An acronym for: Population, Intervention (indicator/exposure/diagnostic tool), Comparison/control, and Outcome. PICO is often used to generate a clinical question for a review of the health literature.


PRISMA is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. PRISMA focuses on the reporting of reviews evaluating randomized trials, but can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. (PRISMA)


PROSPERO is an international database of prospectively registered systematic reviews in health and social care, welfare, public health, education, crime, justice, and international development, where there is a health-related outcome. (PROSPERO) See this page for other places to register your protocols.


"A systematic review protocol describes the rationale, hypothesis, and planned methods of the review.  It should be prepared before a review is started and used as a guide to carry out the review." (PRISMA)

Reference/Citation Managers

A reference/citation manager is a useful tool when conducting a systematic review, as you can export to, manage, and deduplicate search results within this tool.  Several tools that are popular are EndNote, EndNote Online, Mendeley, and Zotero.  More information can be found here.

Reliability and Validity

In the context of systematic reviews, reliability is measured by the development of, adherence to, and detailed reporting of a planned approach that is laid out in the protocol and can be easily replicated. Validity refers to the extent to which the results are measuring what they are supposed to measure. Systematic reviews report on the internal validity of each included study (risk of bias, methodological errors) and potentially some aspects of external validity, i.e. generalizability, applicability, and feasibility. (Cochrane, "Accessing Context Suitability . . .") 

Risk of Bias

When conducting a systematic review, studies to be included in the review need to be evaluated for risk of bias. Bias can be found in the individual studies but also in the actions of the review authors who are writing the systematic review.   Domains of bias include the randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of reported results. Some tools used for risk of bias assessment include the RoB2 tool for randomized control trials, the ROBINS-I tool for non-randomized studies of interventions, and many non-Cochrane tools. (Cochrane Handbook for Systematic Reviews, version 6.3, 2022. Chapter 8)

Supplementary/Hand Searching

Supplementary or hand searching refers to identifying relevant literature by other means outside of one's search strategy. Methods might include examining specific relevant journals and websites, or "snowballing" by either mining the bibliographies of exemplary articles for other relevant references or looking for other articles that have cited the exemplary articles. (See also

Systematic Search Strategy

A systematic search strategy provides readers with a recipe to reproduce the authors' searches. Think of it as a document that includes the exact terms and search fields used, Boolean operators, and any special features employed, for each database or resource that is searched. Systematic reviews need sensitive search strategies--search strategies that have a high recall for the relevant literature.

For more information see V. Nagendrababu,  P. Dilokthornsakul, P. M. H. Dummer, et. al. (February 2020). Glossary for systematic reviews and meta‐analyses. International Endodontic Journal. Volume53, Issue2: 232-249.


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