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Systematic Review: How to Search
Searching
PICO (Population, Intervention, Comparison, Outcome) is a commonly used tool for formulating focused clinical questions. You can use to PICO to clarify your question, determine search concepts and the type of study that is most appropriate to answer the question type.
Use PICO to determine your search terms and also think about synonyms, abbreviations and spelling variants which might be used by authors.
Check to see if your database uses controlled vocabulary, i.e. MeSH in Medline and check your search terms to see if they have a corresponding control term and add them to your search strategy. You will need to use both keywords and controlled vocabulary to be complete when searching.
N.B. Different databases have their own controlled vocabulary, which means that you will need to remap your terms as you switch between databases.
Document your search strategy as you develop it. This will prevent confusion when you start searching.
Use database accounts to save and run your searches. This will also allow you rerun your searches at a later stage.
Get more information on developing your search strategy from the following guides:
Chapter 6 Searching for Studies gives good advice on formulating a search strategy
Searching for studies: A guide to information retrieval for Campbell Systematic Reviews
Using Search Filters
What are Search Filters?
Search filters are pre-formulated search strategies that can be used to refine your searches in order to find certain kinds of results. You can use them to refine your search by such criteria as study design, age, gender among others.
Search filters are designed for specific databases and interfaces, so make sure that you have the appropriate filter for your search. They are being continually being rerfined and improved, so make sure that you pick the most up to date version.
Using a search filter
Once you have located your filter, you can run it in your database. Each line of the search filter is a separate search on teh database and must be implemented exactly as is laid out in the search filter. Once your have finished you can then "AND" it with you your original search strategy to get your results.
Top Tip: You can save time by saving your search filter from the database search history and then just rerunning it when ever you need to.
Examples of Search Filters
- The InterTASC Information Specialists' Sub-Group Search Filter Resource (ISSG)The InterTASC Information Specialists' Sub-Group Search Filter Resource is a collaborative venture to identify, assess and test search filters designed to retrieve research by study design or focus. The Search Filters Resource aims to provide easy access to published and unpublished search filters. It also provides information and guidance on how to critically appraise search filters, study design filters in progress and information on the development and use of search filters. Inclusion of a search filter is not an endorsement of its validity or a recommendation.
- McMaster / Health Informatics Research Unit HedgesThe Hedges Project, investigates ways to develop and harness search filters ("hedges") that will improve retrieval of scientifically sound and clinically relevant study reports from large, general purpose, biomedical research bibliographic databases including MEDLINE, EMBASE, and PsycINFO.
- Scottish Intercollegiate Guidelines Network (SIGN)SIGN has devised suitable strategies for running each search filter in Ovid implementations of Medline, Embase and CINAHL along with other more specialised databases.
- BMJ Clinical Evidence Study design search filtersSystematic review and RCT search strategies have been designed and tested in-house by BMJ Evidence Centre information specialists.
- Center for Evidence-Based Management (CEBMa)CEBMa has developed a filter that will help researchers identify systematic reviews, meta-analyses and studies with a controlled and/or longitudinal design in ProQuest's ABI/Inform, EBSCO's Business Source Global, Premier & Elite, and APA's PsycINFO.
Where to Search for Primary Studies
Selecting sources to search
The sources you decide to search will depend on your discipline. Here is an initial selection of databases that you might find useful for your systematic review. You can find a more complete of databases by discipline here.
Sources for Health
- Medline (OVID) This link opens in a new windowThe MEDLINE database is widely recognized as the premier source for bibliographic and abstract coverage of biomedical literature. MEDLINE encompasses information from Index Medicus, Index to Dental Literature, and International Nursing, as well as other sources of coverage in the areas of allied health, biological and physical sciences, humanities and information science as they relate to medicine and health care, communication disorders, population biology, and reproductive biology.
- CINAHL Plus with Full Text This link opens in a new windowAn authoritative source of full text and bibliographic information for the professional literature of nursing, allied health, biomedicine, and healthcare, dating back to 1937. Full text material includes nearly 800 journals plus legal cases, clinical innovations, critical paths, drug records, research instruments and clinical trials.
- EMBASE (Elsevier) This link opens in a new windowEMBASE (Excerpta Medica) is a comprehensive bibliographic database that covers the worldwide literature on biomedical and pharmaceutical fields.
- Cochrane Library (Wiley) This link opens in a new windowThe Cochrane Library is a collection of databases that contain high-quality, independent evidence to inform healthcare decision-making. It is available on campus only.
Sources for Human Sciences
- PsycInfo (EBSCO) This link opens in a new windowPsycINFO is the American Psychological Association's (APA) resource for abstracts of scholarly journal articles, book chapters, books, and dissertations. It is the largest resource devoted to peer-reviewed literature in behavioral science and mental health, and contains citations and summaries dating as far back as the 1600s. Ninety-nine percent of its content is peer-reviewed.
- ERIC International (Proquest) This link opens in a new windowERIC, sponsored by the US Department of Education, is the premier national bibliographic database of education literature. ERIC consists of two files: Resources in Education, which covers the document literature, consisting of research reports, curriculum and teaching guides, conference papers, and books; and Current Index to Journals in Education, which covers published journal literature from hundreds of periodicals. ERIC International also includes the Australian Education Index. British Education Index, formerly on the platform, is now available from EBSCO.
- Applied Social Sciences Index and Abstracts (Proquest) This link opens in a new windowApplied Social Sciences Index and Abstracts (ASSIA) is a multidisciplinary bibliographic database that covers health, social services, psychology, sociology, economics, politics, race relations and education. ASSIA currently abstracts over 500 journals published in 16 different countries, including the UK and US. This database is particularly useful for research at the intersections between social science and health information.
- Social Sciences Citation Index (Web of Science) This link opens in a new windowThe Social Sciences Citation Index is a multidisciplinary index to the journal literature of the social sciences.
Grey Literature
- Grey Literature ReportGrey Literature Report is bimonthly publication of The New York Academy of Medicine (NYAM) alerting readers to new grey literature publications in health services research and selected public health topics.
Handsearching
Handsearching journals and conference proceedings can be a useful adjunct to searching electronic databases for at least two reasons: (1) not all trial reports are included in electronic bibliographic databases, and (2) even when they are included, they may not contain relevant search terms in the titles or abstracts or be indexed with terms that allow them to be easily identified as trials