The search strategy for a systematic review needs to be as comprehensive as possible in order to capture all studies relevant to the review question. The strategy also needs to be transparent, rigorous and replicable as it is also published in your review.
The general process in developing a search strategy is:
A useful starting point can be to check the search strategies in published systematic reviews for examples of how searches are structured and assist in keyword development. Your librarian can provide you with assistance in developing search strategies.
Brainstorming keywords for a search strategy for a systematic review is essential. Use the concept table below to help structure your brainstorming process.
A comprehensive search would usually entail a combination of subject headings, plus a wide range of keywords/phrases for each concept. Depending on your topic in social sciences, you might find that keywords/phrases result in a better search than using subject headings.
NOTE! Not all databases will have subject heading searching and for those that do, the subject heading categories may differ between databases. This is because databases classify articles using different criteria.
This example is based on the research question:
What are rehabilitation interventions for older people following a stroke?
Example Medline search
The key fields to search are the:
Title/abstract (narrower) or all fields (broader) - use advanced search to build a search with synonyms for a concept combined with OR
Subject Heading - use the database vocabulary (e.g. MeSH or CINAHL headings) to find the subject term.
| Concept 1 - Stroke | AND | Concept 2 - Older person | AND | Concept 3 - Rehabilitation | |
|---|---|---|---|---|---|
| Title or Abstract | stroke OR "cerebrovascular accident" OR "CVA" | elderly OR "old* person" OR aged OR senior* | "resistance train*" OR "physical activit*" OR exercis* | ||
| OR | |||||
| MeSH |
STROKE |
AGED FRAIL ELDERLY MIDDLE AGED AGED 80, AND OVER |
RESISTANCE TRAINING EXERCISE |
See below for a copy of a concept table to help you plan your search strategy.
Source: Queensland University of Technology systematic review library guide - Search the Literature
Bramer, W. M., de Jonge, G.,B., Rethlefsen, M. L., A.H.I.P., Mast, F., & Kleijnen, J. (2018). A systematic approach to searching: An efficient and complete method to develop literature searches. Journal of the Medical Library Association, 106(4), 531-541. doi:http://dx.doi.org/10.5195/jmla.2018.283
Depending on your review question, you need to consider searching both multidisciplinary and subject-specific databases to ensure your search is comprehensive. Multidisciplinary databases such as Web of Science and Scopus contain a high volume of literature from a diverse range of subjects. They are helpful in locating literature on your topic from disciplines you might not have considered. On the other hand, subject-specific databases contain in-depth coverage of literature which is highly specific to a field. A balance of both databases is required in your search strategy.
For subject-specific databases that are relevant to your topic, ask your librarian for advice or for a comprehensive list of databases, check the Library's A-Z list of databases and refine by subject.
Databases which are commonly used for searching in health and social sciences include:
Source: The University of Sydney library systematic review guide
Translating your search across databases: There is a quick guide from Flinders University Library, for search examples across various databases view the University of South Australia guide and a comprehensive guide by ACU Library is below.
Searches for studies should be as extensive as possible in order to reduce the risk of publication bias and to identify as much relevant evidence as possible. Grey literature is unpublished material or has been distributed outside mainstream commercial publishing.
It may include reports, theses, government and non-government organisation publications, conference abstracts and proceedings, registries of clinical trials and prospective studies, and the results of hand searching or corresponding directly with authors.
You might even consider hand searching the contents pages of all issues of a select set of highly relevant journals. Searching grey literature is supported/mandated by the Cochrane Collaboration, the Campbell Collaboration, JBI and the Institute of Medicine (U.S.).
There is a comprehensive guide available from the University of South Australia on Grey Literature and other sources.
Seek assistance from your librarian if further questions.
These resources are a good starting point in your search for grey literature.
View Institutional Repositories at Australian Universities to explore a range of open access resources.
Cochrane advises:
It is important to evaluate and appraise grey literature due to the variability of sources as some documents may not have been peer reviewed and the quality can vary. A possible checklist for evaluating grey literature is using AACODS (Authority, Accuracy, Coverage, Objectivity, Date and Significance).
Reporting on a grey literature search is not as straightforward as for a bibliographic database. Where possible you should aim to record the following information:
Bonato, S. (2018). Searching the grey literature : a handbook for finding annual reports, working papers, white papers, government documents, and more. Rowman & Littlefield Publishers.
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):191. https://doi.org/10.1186/s13643-016-0371-9
CADTH. (2019). Grey Matters: a practical tool for searching health-related grey literature.
CADTH. (2013). Finding the Evidence: Literature Searching Tools in Support of Systematic Reviews.
Canberra University has an extensive Library Guide to Grey Literature in health.
Flinders University has a useful short video to finding grey literature (1:04)
There comes a point where the rewards of further searching may not be worth the the effort needed to capture additional references. The call to abort further searching depends on the question a review addresses and the resources that are available. Check the resources below for more information:
The Cochrane handbook When to stop searching 4.4.11
The PRESS Peer Review of Electronic Search Strategies provides a set of recommendations and a checklist which can be used to evaluate electronic search strategies.
McGowan, J., Sampson, M., Salzwedel, D.M., Cogo, E., Foerster, V, Lefebvre C. (2016). PRESS Peer Review of Electronic Search Strategies: 2015 guideline statement. Journal of Clinical Epidemiology, 75:40-6. https://doi.org/10.1016/j.jclinepi.2016.01.021
When conducting a systematic review, your aim is to search enough databases to be able to state with confidence that the literature has been comprehensively searched. Indicators of a comprehensive search strategy include:
Source: The University of Sydney Library Systematic review guide
A search filter is a defined search strategy designed to find certain types of articles in a particular database. These search filters have been tested by experts and are a quick method of applying a search in the areas below.
CareSearch Australia: find evidence-based literature via PubMed for palliative care and related topics
Integrated care: search integrated care literature via PubMed
Aboriginal and Torres Strait Islander Health: search for literature about ATSI populations and health issues via PubMed
Search Blocks (Biomedische Informatie): add 'blocks' to your database searches to limit them by topic