As mentioned in Step 1, it's a good idea to do some rough preliminary searching before you start your systematic approach. This will help with identifying key authors and keywords and come up with a very few articles which seem important to your topic. These key articles will become your "gold set" which you can not only use to identify search terms, but down the track can help you test your final search strategy. If these articles don't come up when you test your strategy in the databases, you must be missing something.
If you haven't searched in databases for a while (or you are inexperienced), it would be a good idea to refresh yourself on some common useful search techniques. See our Library Resource Guide on Database help, especially the Search Techniques section for a reminder on using boolean operators (AND, NOT, OR), wildcards and truncation, phrase and field searching, and more.
Back in Step 1, you formulated your research question and may have used a search framework to help you do this. The framework (and the question itself) will direct you to the main two or three concepts you need to search. For each concept you will need to consider all the different terms that could be used to describe it. Use your own knowledge of the topic along with words and phrases from preliminary searching you have done to come up with these. Also consider some text mining, or the use of subject dictionaries to identify all possible search terms to use.
For example, using the scenario we described earlier, “Does cranberry juice help reduce urinary tract infections in people living in aged care facilities?”
|Framework element||Concept||Possible search terms|
|P (Population)||People living in aged care facilities||Aged OR elderly OR frail OR ...|
|I (Intervention)||Cranberry juice||Cranberr* OR Vaccinium OR ...|
|C (Comparison)||no cranberry juice|
|O (Outcome)||Urinary tract infection prevention||"Urinary tract infection*" OR UTI OR ...|
Note the use here of phrase searching (usually " ") and truncation symbols (most often *). Some databases use different symbols and some other techniques. Check our Database Help guide for specific instructions.
Once you've come up with as many specific terms as you can find and you are in the database, take one concept at a time, using OR between synonyms. At the end, link the big groups of each concept with the AND operator.
Usually you would not include every framework element in your search strategy. Here we have left out the Comparison element as there is no clear comparative intervention. Often the Outcome is left out because it comes out of all the found studies in any case, and may restrict the scope of the search. In many cases, two of the concepts you choose to search may come from the same framework element. The concepts for searching don't always align exactly with the framework - its purpose is to clarify your question and your concepts.
It's important for any literature search to consider the limitations of your search. For systematic reviews it is vital that you establish the boundaries very early on. Which studies will be excluded from the review and why?
For a systematic review, information about the inclusion and exclusion criteria is usually recorded as a paragraph or table in the methods section (as well as in the Protocol).
Common criteria include: