PICO is a good framework to help clarify your systematic review question.
P - Patient, Population or Problem: What are the important characteristics of the patients &/or problem?
I - Intervention: What you plan to do for the patient or problem?
C - Comparison: What, if anything, is the alternative to the intervention?
O - Outcome: What is the outcome that you would like to measure?
A well constructed search strategy is the core of your systematic review and will be reported on in the methods section of your paper. The search strategy retrieves the majority of the studies you will assess for eligibility & inclusion. The quality of the search strategy also affects what items may have been missed. Informationists can be partners in this process.
For a systematic review, it is important to broaden your search to maximize the retrieval of relevant results.
Use keywords: How other people might describe a topic?
Identify the appropriate index terms (subject headings) for your topic.
Include spelling variations (e.g., behavior, behaviour).
Both types of search terms are useful & both should be used in your search.
Keywords help to broaden your results. They will be searched for at least in journal titles, author names, article titles, & article abstracts. They can also be tagged to search all text.
Index/subject terms help to focus your search appropriately, looking for items that have had a specific term applied by an indexer.
Boolean operators let you combine search terms in specific ways to broaden or narrow your results.
An example of a search string for one concept in a systematic review.
In this example from a PubMed search, [mh] = MeSH & [tiab] = Title/Abstract, a more focused version of a keyword search.
A typical database search limit allows you to narrow results so that you retrieve articles that are most relevant to your research question. Limit types vary by database & include:
In a systematic review search, you should use care when applying limits, as you may lose articles inadvertently. For more information, see, particularly regarding language & format limits. Cochrane 2008 6.4.9