This guide was adapted from Cornell University's Guide to Evidence Synthesis, the University of Minnesota's Systematic Review and Evidence Synthesis, and Northwestern University's Evidence Synthesis & Systematic Reviews.
Your database selection will depend on your research question and the disciplines in which relevant research has been conducted. Every database is different and will require a different search syntax. Some databases have specific controlled vocabulary and thesauri that you will want to incorporate into your searches. It is best to create a master search strategy and then translate it for each database you use. Librarians can help you with database selection and with understanding the specific features of each database.
To begin your database selection, you can use the A-Z Database list or the librarian-created resource guides.
Grey literature is information produced outside of traditional academic publishing and distribution channels. Examples of grey literature include reports, working papers, theses and dissertations, policy literature, newsletters, government documents, conference proceedings, and white papers.
The intent of a systematic review is to synthesize all available evidence that is applicable to your research question. There is a strong bias in academic publishing toward publishing studies that show some sort of significant effect. Meanwhile, many studies and trials that show no effect end up going unpublished. But knowing that an intervention had no effect is just as important as knowing that it did have an effect when it comes to making decisions for practice and policy-making. While not peer-reviewed, grey literature represents a valuable body of information that is critical to consider when synthesizing and evaluating all available evidence.
Finding grey literature and searching it systematically is challenging. But there are a few approaches that you can take to add some structure to your search of this type of information.
Be sure to record and document your search as you go along to ensure you don't have to recreate your work later.
Sources for grey literature searches will vary by discipline; the links below are some of the more common resources used, but this is in no way a comprehensive list.
Open-access archive for scholarly articles in STEM and business from Cornell University.
Dissertations and theses from around the world. 1861 to present.
Contains records for more than 1.4 million electronic theses and dissertations from more than 320 universities around the world.
Index of papers presented at worldwide conferences. From the British Library Document Supply Centre's (BLDC) proceedings collection.
In an evidence synthesis search, the goal is to collect all potentially relevant material that is available in your search. Missing relevant studies can lead to bias or incorrect conclusions. There are several steps to take to develop a comprehensive search strategy.
Documentation is essential while designing and running your searches. This ensures the rigor of your research, provides documentation, and minimizes bias. At a minimum, your documentation should include:
The most common reporting standard for the search process is PRISMA-S. The PRISMA diagram summarizes the flow of records through the search, screening and synthesis stages.
As mentioned above, you will need to search multiple databases to get a comprehensive look at your topic, and not all databases use the same search "syntax." Because of this, you will need to translate your strategies to work with each specific database.
For example, a search for vitamin D[tiab] in PubMed will show you all citations with the phrase "vitamin D" in the title, abstract, or keywords, but a search for vitamin D[tiab] in Web of Science will not work at all.
Begin by creating and testing your search strategy on a primary database, typically one which has a robust thesaurus or controlled vocabulary. Each database will have its own thesaurus/controlled vocabulary (or not have one at all), so it is important to explore and adjust accordingly.
There are several tools available online to help you with search strategy and translation; you can find these below or in the Tools tab on the left.
