Identifying research evidence
Systematic reviews require a comprehensive and reproducible search of a wide range of sources to identify as many relevant studies as possible. An exhaustive search process minimizes the risk of biased reporting of results and thereby strengthens the validity and trustworthiness of the review.
Literature searching is an iterative process so be prepared to work on and refine your search strategy as you go; it may take a few iterations of the search to get it right. Please make sure you allocate enough time to first create and review the effectiveness of your search strategies.
Typically, identifying research evidence to include in systematic reviews encompasses the following:
There are a number of methods used to identify published and unpublished data including:
See below for more information on the range of healthcare databases you can access, library database help-sheets and guides, and scoping searches.
The healthcare databases
There are a number of healthcare and social care databases available to track down published literature. As no single database is completely comprehensive, it’s important to search as many databases as possible to capture research from the widest pool of sources. This is a major factor in distinguishing systematic reviews from traditional literature reviews and helps to minimise bias. A search of Medline alone is not enough.
Databases are provided via different platforms or hosts, such as:
The following key databases should be searched for most questions around healthcare interventions:
A paper (Bramer et al, 2017) has also suggested that Google Scholar, Google's academic search engine, is also a useful adjunct to these key databases, but it should not be used to replace traditional databases.
Other databases focus on different population groups or specialties or type of information, and depending on your topic it will also be important to search some of these resources in addition to the ones listed above. These other databases include:
Use the library’s database webpage for an overview of all these databases and more, on-site access links and information about off-site login procedures such as OpenAthens (for NHS users) or Shibboleth/Institutional Login (for SGUL staff and students).
What is a scoping search?
Scoping searches are fairly brief searches of existing literature designed to help you gain an overview of the range and depth of research that exists for a particular research idea.
Scoping searches can also help you identify alternative words and phrases to add to your search strategy.
Databases to consider running basic, initial searches include: