Research Guides: Systematic Reviews & Other Syntheses: Searching for Studies

MEDLINE: Did you know?

You can search MEDLINE using PubMed or the Ovid interface. PubMed is a free resource that you will always be able to access, whereas Ovid MEDLINE is a proprietary resource that has been purchased by Queen's University Library. The Ovid interface and may be more user-friendly for new searchers than PubMed and provides a consistent look and feel if searchers will be accessing other databases on the Ovid platform such as Embase, Cochrane CENTRAL, PsycINFO, Global Health, and AMED.

Cochrane: Did you know?

The library provides access to two different interfaces for searching Cochrane Library: Wiley or Ovid. If your review will only be synthesizing primary studies, there is no need to search all of Cochrane Library (which also includes the Database of Systematic Reviews), instead, limit your search to Cochrane CENTRAL to retrieve trials only.

Introduction

Deciding where to search for studies will largely depend on the review type and topic. A comprehensive search approach is often the goal, as systematic reviews and some other syntheses attempt to identify all evidence for a given research question. Locating studies for syntheses often includes searching for both published and unpublished ("grey") literature.

Studies for your syntheses may be found in the form of:

peer-reviewed journal articles
preprint articles
conference abstracts/papers
dissertations and theses
governmental or private sector research
ongoing or unpublished clinical trials

Library Databases

Bibliographic/citation databases contain bibliographic information (e.g., citation information and abstracts) for sources of literature. The databases compared and listed below predominantly include bibliographic records of journal articles, but some also contain records for conference abstracts/papers, preprints, dissertations, and more.

Queen's University Library provides access to broad coverage databases in the health sciences (such as Ovid MEDLINE and Embase) as well as smaller subject-specific databases (such as PsycINFO and CINAHL). See the Database Comparison further down this page to learn more about some of these databases.

Directly below is a list of the most popular health sciences databases that Queen's has access to. It is not a comprehensive list of potentially relevant databases. Depending on your review topic, it may also be appropriate to search in databases from other disciplines such as the social sciences, law or education. To discover more databases that might be relevant for your topic, try the Browse Databases by Subject feature on the library website or speak with a librarian.

AMED - Allied and Complementary Medicine
The Allied and Complementary Medicine Database (AMED) is a unique bibliographic database produced by the Health Care Information Service of the British Library. It covers a selection of journals in complementary medicine, palliative care, and several professions allied to medicine.
Date Coverage: 1985 -
BIOSIS Previews
Life sciences and biomedical research covering pre-clinical and experimental research, methods and instrumentation, animal studies, and more.

Date Coverage: 1926- present
BIOSIS Previews combines the content of both Biological Abstracts and Biological Abstracts/RRM (Reports, Reviews, Meetings), thus providing comprehensive coverage of nearly 5,500 life science journals as well as 1,500 items from international meetings, review articles, books, book chapters, patents, and software reviews.

Subject coverage: All areas of life science, including such topics as: agriculture, biochemistry, biotechnology, ecology, immunology, microbiology, molecular genetics, neuroscience, pharmacology, public health, toxicology, zoology.

Because Queen's University Library subscribes to both BIOSIS Previews and Web of ScienceÂ®, a link in a full record from BIOSIS will take you to the corresponding record in ISI Web of Science.

Further information: Available on the vendor's website.
CINAHL and Pre-CINAHL
CINAHL provides indexing for more than 6,000 journals from the fields of nursing and allied health. The database contains more than 8 million records, offering complete coverage of English-language nursing journals and publications from the National League for Nursing and the American Nurses’ Association. CINAHL covers nursing, biomedicine, alternative/complementary medicine, consumer health and 17 allied health disciplines.
In addition, this database offers access to health care books, nursing dissertations, selected conference proceedings, standards of practice, educational software, audiovisuals and book chapters. Searchable cited references for more than 1,300 journals are also included.

Bracken Library Database Highlight: CINAHL:

https://youtu.be/UAnQfrw0Acg?si=wr3IH5GMyEV0R8_m

Date Coverage: 1981 - very recent articles
EBM Reviews - Cochrane Central Register of Controlled Trials
Cochrane Central Register of Controlled Trials is a bibliographic database of definitive controlled trials, and part of Ovid's EBM Reviews collection. It contains over 300,000 bibliographic references to controlled trials in health care together with references to clinical trials identified by contributors to the Cochrane Collaboration in MEDLINE and EMBASE. Contributors follow quality control standards to ensure that only reports of definite randomized controlled trials or controlled clinical trials are included. These controlled trials included were identified by the contributors to the Cochrane Collaboration to create an unbiased source of data for systematic reviews.

2-user limit
Cochrane Library
The Cochrane Library is a collection of high-quality, independent evidence to inform healthcare decision-making. The Cochrane Library, published by Wiley, includes:

Cochrane Database of Systematic Reviews - peer-reviewed systematic reviews and protocols from the leading resource for systematic reviews in health care.

Cochrane Central Register of Controlled Trials (CENTRAL) - a highly concentrated source of references to reports of randomized and quasi-randomized controlled trials.

Cochrane Clinical Answers (CCAs) - clinically-focused entry point to rigorous research from Cochrane Reviews. CCAs are designed to be actionable and to inform point-of-care decision-making. Each CCA contains a clinical question, a short answer, and data for the outcomes from the Cochrane Review deemed most relevant to practicing healthcare professionals.

The Cochrane Library can also be searched on the Ovid platform via EBM Reviews. Ovid EBM Reviews also includes ACP Journal Club.
EMBASE
Embase (Excerpta Medica Database) is a biomedical and pharmacological database produced by Elsevier B.V., containing more than 45 million records from over 8,500 journals published world-wide. It contains bibliographic records with citations, abstracts, and indexing derived from articles in peer reviewed journals, articles in preprint servers medRxiv and bioRxiv, and abstracts and papers from over 15,000 conferences. Embase has especially strong in its coverage of drug and pharmaceutical research, pharmacology and toxicology.
Date Coverage: 1947 - present
Global Health
GLOBAL HEALTH brings together the resources of two internationally renowned databases - the Public Health and Tropical Medicine (PHTM) database, previously produced by the Bureau of Hygiene and Tropical Diseases (BHTD), and the human health and diseases information extracted from CAB ABSTRACTS.
The Global Health database covers the following aspects of human health and disease:

communicable diseases (including HIV/AIDS)
tropical diseases, i.e, diseases in the tropics (including field and experimental studies)
parasitic diseases and parasitology - medical entomology
human nutrition (including food composition, food poisoning, effects of diet on health, nutritional disorders, and experimental aspects)
community and public health (including chronic diseases, occupational health, health status indicators, the impact of agriculture on health, and cancer epidemiology)
medicinal and poisonous plants (including pharmacology, tissue culture, animal studies, plant composition, allergens, and toxins)

Date coverage: 1910 - present
MEDLINE
Ovid MEDLINE database contains more than 38 million references to biomedical and life sciences literature. The primary component of Ovid MEDLINE is MEDLINE, which is produced by the National Library of Medicine in the U.S. and contains more than 31 million references from over 5,200 scholarly journals published around the world. In addition to MEDLINE content, Ovid MEDLINE includes citations that are being processed for MEDLINE, citations that are out-of-scope from MEDLINE journals, "ahead of print" citations that precede the article's final publication in a MEDLINE journal, and more.

The same content in Ovid MEDLINE can also be searched in PubMed.

Bracken Library Database Highlight: Ovid MEDLINE
Date Coverage: 1946 to Present
APA PsycInfo [via Ovid]
APA PsycInfo® is an electronic bibliographic database providing abstracts and citations to the scholarly literature in the psychological, social, behavioral, and health sciences. The database includes material of relevance to psychologists and professionals in related fields such as psychiatry, management, business, education, social science, neuroscience, law, medicine, and social work. Updated weekly, APA PsycInfo® provides access to journal articles, books, chapters, and dissertations.
REF BF1.P94 1927-1995 (Psychological Abstracts)

Date Coverage: 1806-present
PubMed
PubMed is a free literature database that contains more than 38 million references to biomedical and life sciences literature. The primary component of PubMed is MEDLINE, which is produced by the National Library of Medicine in the U.S. and contains more than 31 million references from over 5,200 scholarly journals published around the world. In addition to MEDLINE content, PubMed includes citations that are being processed for MEDLINE, citations that are out-of-scope from MEDLINE journals, "ahead of print" citations that precede the article's final publication in a MEDLINE journal, and more. Mobile access is available for PubMed.

The same content in PubMed can also be searched in Ovid MEDLINE .

Bracken Library Database Highlight: CINAHL

Date Coverage: 1946 – present
Scopus
Scopus is the largest abstract and citation database, including peer-reviewed titles from international publishers, Open Access journals, conference proceedings, trade publications, quality web sources.
Date Coverage: 1788-present (updated daily)
Web of Science (Core Collection)
A large, multidisciplinary database, Web of Science provides access to bibliographic information, author abstracts, and cited references from scholarly journals and conference proceedings. A cited reference search enables you to find articles that cite a previously published work.
This database consists of these subject components, which can be searched simultaneously or individually (to search individually, limit to required citation database(s) at bottom of screen):

Science Citation Index Expanded - science and technology journals from 1900-present
Social Sciences Citation Index - social sciences journals from 1956-present
Arts & Humanities Citation Index - arts and humanities journals from 1975-present
Conference Proceedings Citation Index - Science (CPCI-S) from 1990-present
Conference Proceedings Citation Index - Social Science & Humanities (CPCI-SSH) from 1990-present
Journal Citation Reports (listing impact factors and other journal performance metrics) are available through Web of Science.

Science Citation Index: 1900 - present ; Social Sciences Citation Index: 1956 - present ; Arts and Humanities: 1975 - present

Database Comparison

	PubMed/ Ovid MEDLINE	Embase	CINAHL	PsycINFO	Cochrane Library	Web of Science	BIOSIS Previews
Years:	1946- present	1947-present	1980- present	1806- present	Varies by database	1900- present	1926- present
Journals:	>6,500	> 8,500	>3,100	>2,500	N/A	>33,000	>5,500
Records:	> 38 million	> 45 million	~8 million	> 5 million	>1 million	>92 million	> 18 million
Record Types:	Mainly journal articles	Journal articles, conference abstracts/papers, preprints	Journal and magazine articles, dissertations, books	Journal articles, book chapters, dissertations	High-quality controlled trials and systematic reviews	Journal articles, book chapters, conference proceedings	Journal articles, book chapters, conference proceedings, patents
Subjects Included:	Biomedicine incl. allied health, biological and physical sciences and humanities	Biomedicine, pharmacology, toxicology, life sciences, and healthcare admin	Nursing, biomedicine, allied health and alternative medicine	Psychological literature incl. social, behavioral, and health sciences	Evidence for healthcare interventions and diagnostic assessment	Multidisciplinary incl. science, technology, education, humanities & social sci	Life sciences: biotechnology, neuroscience, pharmacology, toxicology, and zoology
Subject Headings:	MeSH	Emtree	CINAHL Subject Terms	APA Thesaurus Terms	MeSH, but only for some records	N/A	N/A
QUL Platforms:	Ovid and PubMed	Ovid	Ebsco	Ovid and APA PsycNET	Ovid and Wiley	Web of Science	Web of Science
Notes:	No need to search both Ovid MEDLINE and PubMed				Aka Ovid EBM Reviews

Hand-Searching

Journals

Hand-searching relevant journals page by page can be incredibly time-consuming but it may identify additional studies that have been missed by database search strategies or studies from journals that are not covered in electronic databases.

Research evidence:

A systematic review by Hopewell et al. (2007) on the efficacy of handsearching to identify reports of randomized trials found that "...a combination of handsearching and electronic searching is the most comprehensive approach in identifying reports of randomized trials" (p. 2). However, the authors noted "...where time and resources are limited, searching an electronic database using a complex search will identify the majority of trials published as full reports in English language journals, provided, of course, that the relevant journals have been indexed in the database" (p. 2).

Conference proceedings

Databases may not index conference proceedings, and even if they do, coverage may be limited. Hand-searching relevant conference proceedings that are available on association or conference websites may identify additional relevant studies.

Searching Reference Lists

Once you have identified eligible studies for your knowledge synthesis by searching the appropriate resources above, it is best practice to then check the reference lists of these studies to identify any additional studies. The reference lists of related reviews may also help to identify additional studies.

Research evidence:

A systematic review was conducted by Horsley et al. (2011) to determine whether searching reference lists actually identifies additional studies during the systematic review process. Most studies included in their systematic review reported that this practice did identify additional studies; however, the evidence supporting this practice most often came from case report data and not high quality research. Despite this, Horsley et al. still recommend that systematic reviewers screen the reference lists of relevant studies to find additional studies, especially when you're struggling to find relevant information.

Cited Reference Searching

Citation indexes such as Web of Science (or the search engine Google Scholar) can be used for cited reference searching. Citation reference searching allows you to identify where eligible studies have later been cited to see if this identifies any additional studies.

For example, if you search for a relevant study in Google Scholar you will see a "Cited by..." link underneath the study information that indicates how many times the study has been cited (unless the study has not yet been cited). You can follow this link to view where the study has been cited to see if this locates any additional studies.

Bibliography

Cooper, C., Lovell, R., Husk, K., Booth, A., & Garside, R. (2017). Supplementary search methods were more effective and offered better value than bibliographic database searching: a case study from public health and environmental enhancement. Research Synthesis Methods, (October 2017), 195–223.

Craven, J. and P. Levay (2019). Systematic Searching: Practical Ideas for Improving Results, Facet Publishing.

Hartling, L., Featherstone, R., Nuspl, M., Shave, K., Dryden, D. M., & Vandermeer, B. (2016). The contribution of databases to the results of systematic reviews: a cross-sectional study. BMC Medical Research Methodology, 16.

Hopewell, S., Clarke, M., Lefebvre, C., & Scherer, R. (2007). Handsearching versus electronic searching to identify reports of randomized trials. Cochrane Database of Systematic Reviews, 2.

Horsley, T., Dingwall, O., & Sampson, M. (2011). Checking reference lists to find additional studies for systematic reviews. Cochrane Database of Systematic Reviews, 10(8).

Lefebvre C., Glanville J., Briscoe S., Littlewood A., Marshall C., Metzendorf M.-I., Noel-Storr A., Rader T., Shokraneh F., Thomas J. & Wieland L.S. Chapter 4: Searching for and selecting studies. In: Higgins J.P.T., Thomas J., Chandler J., Cumpston M., Li T., Page M.J. & Welch V.A. (Eds). Cochrane Handbook for Systematic Reviews of Interventions version 6.0 (updated July 2019). Cochrane, 2019. Available from www.training.cochrane.org/handbook.

Lefebvre, C., Glanville, J., Wieland, L. S., Coles, B., & Weightman, A. L. (2013). Methodological developments in searching for studies for systematic reviews: past, present and future? Syst Rev, 2(1), 78.

McAuley, L., Pham, B., Tugwell, P., & Moher, D. (2000). Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses? The Lancet, 356(9237), 1228–1231.

Papaioannou, D., Sutton, A., Carroll, C., Booth, A., & Wong, R. (2009). Literature searching for social science systematic reviews: consideration of a range of search techniques. Health Information & Libraries Journal, 27(2), 114–122.

Schmucker, C. M., Blümle, A., Schell, L. K., Schwarzer, G., Oeller, P., Cabrera, L., … Consortium, on behalf of the O. (2017). Systematic review finds that study data not published in full text articles have unclear impact on meta-analyses results in medical research. PLOS ONE, 12(4).

Stansfield, C., Dickson, K., & Bangpan, M. (2016). Exploring issues in the conduct of website searching and other online sources for systematic reviews: how can we be systematic? Systematic Reviews, 5(1).