Developing your search strategy is key to ensuring that you find the right kind of evidence for your systematic review. Your search strategy refers to the specific keywords and connectors you will use to find relevant literature. Revisiting your research question will help you determine the relevant terms. Search strategies for systematic reviews can be incredibly complex, and require you to have knowledge of searching techniques such as Boolean logic (the use of AND, OR, NOT to connect terms together). A sample search strategy for our earlier example would involve the following key concepts:
handwashing OR hand sanitizing OR hand hygiene
Depending on which databases you are searching, you may have to vary your keywords to reflect the particular requirements of a specific database. Some databases may use a controlled vocabulary, which will require you to use different search terms, e.g. MEDLINE
Once you have developed your search strategy, you'll need to identify what information resources you plan to search for evidence. This can include scholarly publications such as peer-reviewed journal articles or books, as well as grey literature that is not formally published, such as theses/dissertations, or conference proceedings (databases such as Scopus or Web of Science include citations to conference proceedings). You should look at your inclusion/exclusion criteria again, as this will help determine what types of information sources you should be searching. You also may have already identified some of the key information sources in your protocol document, if you completed one.
The Library subscribes to many subject databases that will allow you to identify journal articles and other sources that will be useful for your review. You may also want to consider searching some specialized databases for specific types of material, such as theses/dissertations or government documents. You can search multiple databases to ensure as thorough a search as possible, but consider your timelines as well.
Hand searching could include scanning the tables of contents of key journals in the field, or looking at important papers related to the topic, and searching their reference lists for other relevant sources - the latter is sometimes described as 'snowballing'.