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Knowledge Syntheses: A How-To Guide

Overview of systematic review steps and resources to assist researchers conducting reviews

Your Search Process

Developing comprehensive, reproducible, and transparent searches takes time. The full search process for your systematic review might look something like this:

Preliminary Searches (non-systematic)

Conducting some preliminary, non-systematic searches on your topic will help you to:

  • help identify key terms and synonyms;
  • find existing systematic reviews on any component of your topic and review search strategies included in methods or appendix; and
  • locate some target, likely to be included, articles (aka "seed" articles) through non-systematic searching (using related articles functions, basic searching, etc.).
Overall Final Comprehensive Search Process (systematic)

When you are ready to conduct your systematic search, consider the following process:

  1. Identify terms for each concept (use "seed" articles identified from preliminary searching/concept exploration)
    • Also discuss best sources to search with a librarian (e.g. PubMed, Embase, CINAHL, Cochrane, etc.)
  2. Develop and run search in first database
  3. Test and refine search based on retrieval (Tip: use target articles identified in preliminary searches to confirm sensitivity of search; discuss and determine precision/sensitivity tolerance based on available resources for completing review)
  4. Seek feedback or peer review of search strategy
  5. Translate search to other database(s)
  6. Compile results from all databases and remove duplicates to prepare for screening
  7. As studies to include emerge from the screening process, check the references and whether the included study has been cited (use CitationChaser tool:
  8. Determine relevant grey literature sources and search with modified strategies (includes trial registries, conference proceedings, theses and dissertations, etc.)
  9. Contact experts, including corresponding authors of included studies, to find out about additional or ongoing studies
  10. Hand search additional non-indexed journals or conference proceedings, if appropriate
  11. Update search if significant time elapsed since initial search

Document entire search process

Follow the PRISMA-S guidelines for reporting searches in comprehensive reviews to describe the search process.

Systematic Searching

Systematic searching requires a set of skills and techniques that you may not have encountered in your previous research. In addition to guiding you to key databases and other sources of information, these pages offers some tips on systematic search methods.

The concept map form above can be useful for keeping track of your brainstorming of terms to search on each concept of your research question.

Information Sources to Search


Health Science Databases*

Interdisciplinary Databases *

* For other recommendations of databases for a specific discipline, check out the relevant subject guide

Grey literature is literature produced by any organisation whose central purpose is not publishing. These organisations include governments, businesses, not-for-profits, health organisations and associations, and more. Searching for grey literature can be difficult because it is not usually indexed within traditional databases. When completing a systematic review, however, it is imperative to find as much evidence as possible, and that means searching beyond academic literature alone.

See: Hartling L, Featherstone R, Nuspl M, Shave K, Dryden DM, Vandermeer B. Grey literature in systematic reviews: a cross-sectional study of the contribution of non-English reports, unpublished studies and dissertations to the results of meta-analyses in child-relevant reviews. BMC Medical Research Methodology. 2017 Apr 19;17(1):64.


Grey Lit Searching Checklists


Selected Grey Literature Sources


Search Translation Resources

Search Tutorial Videos

Search Filters

Search filters, sometimes called hedges, are strings of search terms that are used to limit search results. Many databases feature a built-in set of search filters that are commonly used to limit search results by age group, publication type, study type, and more.

When conducting a systematic review, however, there is a possibility that these filters may exclude relevant studies. For this reason, search experts and institutions have developed their own search filters, and many are available online for public use.

Randomized Controlled Trials

From the Cochrane Handbook, Section 6.4.11, Box 6.4.a:

(((((((((randomized controlled trial [pt]) OR controlled clinical trial [pt]) OR randomized [tiab]) OR placebo [tiab]) OR drug therapy [sh]) OR randomly [tiab]) OR trial [tiab]) OR groups [tiab])) NOT ((animals [mh] NOT humans [mh])) 

From Glanville, J. M., Lefebvre, C., Miles, J. N. V., & Camosso-Stefinovic, J. (2006). How to identify randomized controlled trials in MEDLINE: ten years on. Journal of the Medical Library Association94(2), 130–136.:

(((((((clinical trial[pt]) OR randomized[tiab]) OR placebo[tiab]) OR clinical trials[mh]) OR randomly[tiab]) OR trial[ti])) NOT ((animals[mh]) NOT (animals[mh] AND humans[mh])) 

Qualitative Studies

From University of Texas School of Public Health:

“interviews as topic”[Mesh:noexp] OR “focus groups”[Mesh:noexp] OR narration[Mesh:noexp] OR qualitative research[Mesh:noexp] OR (((“semi-structured”[TIAB] OR semistructured[TIAB] OR unstructured[TIAB] OR structured[TIAB] OR informal[TIAB] OR “in-depth”[TIAB] OR indepth[TIAB] OR “face-to-face”[TIAB] OR guide[TIAB] OR guides[TIAB]) AND (interview*[TIAB] OR discussion*[TIAB] OR questionnaire*[TIAB])) OR (“focus group”[TIAB] OR “focus groups”[TIAB] OR qualitative[TIAB] OR ethnograph*[TIAB] OR fieldwork[TIAB] OR “field work”[TIAB] OR “key informant”[TIAB]))

Systematic Reviews

Adapted from SIGN:

((((((((((("Meta-Analysis as Topic"[Mesh]) OR meta analy*[tw]) OR metaanaly*[tw]) OR Meta-Analysis[pt]) OR (((systematic AND (review* OR overview*)) AND tw))) OR "Review Literature as Topic"[Mesh])) OR ((((((((cochrane[tiab]) OR embase[tiab]) OR ((psychlit OR psyclit[tiab]))) OR ((psychinfo OR psycinfo[tiab]))) OR ((cinahl OR cinhal[tiab]))) OR science citation index[tiab]) OR bids[tiab]) OR cancerlit[tiab])) OR (((((reference list*[tiab]) OR bibliograph*[tiab]) OR hand-search*[tiab]) OR relevant journals[tiab]) OR manual search*[tiab])) OR ((((selection criteria[tiab]) OR data extraction[tiab])) AND "Review"[pt]))) NOT (((("Comment"[pt]) OR "Letter"[pt]) OR "Editorial"[pt]) OR (("Animals"[Mesh]) NOT (("Animals"[Mesh] AND "Humans"[Mesh])))) 

Randomized Controlled Trials

From University of Alberta:

( (MH "Random Assignment") or (MH "Random Sample+") or (MH "Crossover Design") or (MH "Clinical Trials+") or (MH "Comparative Studies") or (MH "Control (Research)+") or (MH "Control Group") or (MH "Factorial Design") or (MH "Quasi-Experimental Studies+") or (MH "Placebos") or (MH "Meta Analysis") or (MH "Sample Size") or (MH "Research, Nursing") or (MH "Research Question") or (MH "Research Methodology+") or (MH "Evaluation Research+") or (MH "Concurrent Prospective Studies") or (MH "Prospective Studies") or (MH "Nursing Practice, Research-Based") or (MH "Solomon Four-Group Design") or (MH "One-Shot Case Study") or (MH "Pretest-Posttest Design+") or (MH "Static Group Comparison") or (MH "Study Design") or (MH "Clinical Research+") ) or ( clinical nursing research or random* or cross?over or placebo* or control* or factorial or sham* or meta?analy* or systematic review* or blind* or mask* or trial* )


Systematic Reviews

From University of Texas School of Public Health:

(TI (systematic* n3 review*)) or (AB (systematic* n3 review*)) or (TI (systematic* n3 bibliographic*)) or (AB (systematic* n3 bibliographic*)) or (TI (systematic* n3 literature)) or (AB (systematic* n3 literature)) or (TI (comprehensive* n3 literature)) or (AB (comprehensive* n3 literature)) or (TI (comprehensive* n3 bibliographic*)) or (AB (comprehensive* n3 bibliographic*)) or (TI (integrative n3 review)) or (AB (integrative n3 review)) or (JN “Cochrane Database of Systematic Reviews”) or (TI (information n2 synthesis)) or (TI (data n2 synthesis)) or (AB (information n2 synthesis)) or (AB (data n2 synthesis)) or (TI (data n2 extract*)) or (AB (data n2 extract*)) or (TI (medline or pubmed or psyclit or cinahl or (psycinfo not “psycinfo database”) or “web of science” or scopus or embase)) or (AB (medline or pubmed or psyclit or cinahl or (psycinfo not “psycinfo database”) or “web of science” or scopus or embase)) or (MH “Systematic Review”) or (MH “Meta Analysis”) or (TI (meta-analy* or metaanaly*)) or (AB (meta-analy* or metaanaly*))

Randomized Controlled Trials

Adapted from the Cochrane Handbook by the Cochrane Occupational Health and Safety Group:

'crossover procedure':de OR 'double-blind procedure':de OR 'randomized controlled trial':de OR  'single-blind procedure':de OR (random* OR  factorial* OR crossover* OR cross NEXT/1 over* OR placebo* OR doubl* NEAR/1 blind* OR singl* NEAR/1 blind* OR assign* OR allocat* OR volunteer*):de,ab,ti

Adapted from SIGN by the Cochrane Occupational Health and Safety Group:

'clinical trial'/de OR 'randomized controlled trial'/de OR 'randomization'/de OR 'single blind procedure'/de OR 'double blind procedure'/de OR 'crossover procedure'/de OR 'placebo'/de OR 'prospective study'/de OR 'randomi?ed controlled' NEXT/1 trial* OR rct OR 'randomly allocated' OR 'allocated randomly' OR 'random allocation' OR allocated NEAR/2 random OR single NEXT/1 blind* OR double NEXT/1 blind* OR (treble OR triple) NEAR/1 blind* OR placebo*

Qualitative Studies

Adapted from McMaster HIRU:

interview:de,ab,ti OR 'health care organization'/exp OR experiences:de,ab,ti


Cochrane Highly Sensitive Search Strategy for identifying randomized trials in MEDLINE: sensitivity-maximizing version (2008 revision); Ovid format

1 randomized controlled
controlled clinical
drug therapy.fs.
1 or 2 or 3 or 4 or 5 or 6 or 7 or 8
exp animals/ not
9 not 10

From: Lefebvre C, Glanville J, Briscoe S, Featherstone R, Littlewood A, Marshall C, Metzendorf M-I, Noel-Storr A, Paynter R, Rader T, Thomas J, Wieland LS. Technical Supplement to Chapter 4: Searching for and selecting studies. In: Higgins JPT, Thomas J, Chandler J, Cumpston MS, Li T, Page MJ, Welch VA (eds). Cochrane Handbook for Systematic Reviews of Interventions Version 6.3 (updated February 2022). Cochrane, 2022. Available from:, Box 3.c


Search tools and visualization

Knowledge Synthesis Search Timeline