A systematic review search aims for comprehensiveness in order to have the widest, relevant pool from which to select studies for analysis. This also helps to reduce potential bias by aiming to review and select from all known studies about the topic using your pre-established eligibility criteria, and following your study protocol.
If you are new to advanced searching and would like to learn more, the University of Michigan's edX course on Advanced Literature Searching in the Health Sciences is a great place to start! For a quick lesson on searching basics, check out Monash University's tutorial on Developing a Search Strategy.
"Expert searchers are an important part of the systematic review team, crucial throughout the review process from the development of the proposal and research question to publicaiton." (McGowan & Sampson, 2005)
We use the PRESS Guidline and Checklist to consult with you on designing and then reviewing your systematic review search strategy. McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 guideline statement. J Clin Epidemiol. 2016 Jul;75:40-6. http://www.sciencedirect.com/science/article/pii/S0895435616000585
Note: As with all steps, check the guideline / protocol you are using to ensure you meet information source and search requirements.
When conducting a systematic review, it is important to create an effective search statement, and search multiple databases that cover your topic area to ensure you have conducted a comprehensive search to find as many relevant information sources as possible.
Use the "Subject Guides" provided by the University Libraries to locate key databases. As these guides are intended to be used as starting points for research, consult with the subject librarian to determine what other databases would be useful for your topic.
When you select a database to choose, make sure to record:
When you conduct your search, make sure to record:
As access to database content by name, provider, and years covered vary by institution; and methods for conducting a search within a given database also vary, these pieces of information are crucial for other researchers to know, particularly if they are trying to replicate your search.
Managing your search results:
Please note that the University Libraries and our vendors implement download limits that you may encounter when attempting to perform a comprehensive search. Find more information about these limits on our Collections Management Policy LibGuide. We know these limitations can be frustrating, but they are here to protect services for all users. If you encounter problems with these limits, please don't hesitate to reach out to us email@example.com.
Once you have developed keywords and terms that will help you identify and focus on more specific aspects of your topic, it’s helpful to create a search strategy that can be used to combine your terms using the Boolean operators AND and OR to search databases.
If you have not used Boolean operators in the past, or want to know what other tools you can use, read the information below. If you have used them in the past, then use the Search Strategy Builder link below to create a search strategy. Make sure you put your synonyms in the like-colored columns for each concept you wish to tie together.
You can then copy and paste this search strategy into any of the databases as well as Google and Google Scholar.
In addition to Boolean operators, here are a few other tools you can use as you build your search statements:
Wouldn't it be great if there was a way to search for variations of a word so you didn't have to type OR all the time? Good news, there is! The most common symbol used to add characters after a root word is the asterisks (*). To use this, simply put the * at the end of your word, and the database will look for the root word, along with any letters that follow. Be careful though, if your root word is too short, you'll get a lot of things that don't relate. For example:
forest* will find:
|vet* will find:|
There are other truncation symbols you can use within words as well. Check the "help" section of the database to see what other symbols are supported by that particular database and how they can be used.
What if you need to search for a phrase? You dictate that your terms must be found right next to each other and in the order you write them in simply by putting two or more words in quotation marks. For example:
What if you want to use more than one Boolean operator and more than one of the above tools? It is very easy to combine Boolean operators, but as this follows a logical system, you must include parentheses to dictate order of operations. For example, while the following two searches use the same terms and the same Boolean operators in the exact same order, they'll return very different numbers of results based on how the search was interpreted (bold and colors demonstrate how it will be read by the system):
would be interpreted as: "Blue Ridge mountains" OR "Appalachian Mountains" AND river* OR creek* OR stream* AND pollut*
as the the above will look for records that have the phrase "Blue Ridge mountains" OR... anything that follows; it will look for records that have the phrase and term "Appalachian Mountains" AND river (and all variations: rivers, etc); it will look for records that have the term creek (and all variations: creeks, etc); and it will look for records that have the terms stream (and all variations: streams) and pollution/polluted/polluting (all variations of pollut*).
would be interpreted as: ("Blue Ridge mountains" OR "Appalachian Mountains") AND (river* OR creek* OR stream*) AND pollut*
as this search will look for records that have either (or both) of the phrases "Blue Ridge mountains"/"Appalachian mountains", but it also has to include either of the terms (and the variations of: river/creek/stream, and it has to include any of the variations of the term pollut* (polluted, polluting, pollution, etc) in order to come back in the results list.
It important to locate grey literature sources (conferences, government reports, associations) that also produce literature about your topic.
Start with the databases, as many cover key conferences in a discipline, but search Google and Google Scholar as these are also excellent places to search for this type of information. Look through the first 100-200 results to ensure that you haven't missed anything that would be relevant to your topic.
Boolean operators are very powerful tools that follow a specific logic. They dictate how you want your keywords to be searched, you just have to state how you want them to be used to interpret your terms. The two most commonly used in databases are:
While many databases don't require for them to be capitalized, it is good practice to do so; plus you can quickly glance at your search statement and see where they are. The above are the two most common, but there are other operators you can use. Check the "help" section of the database to see what other operators you can use that are supported by that particular database.