Search Terms and Subject Headings
It is important to choose your search terms/keywords carefully. Is there more than one term for the concept for which you are searching? Are you using a technical term or the layman's version? For example, if you are researching breast cancer, it is also known in the nursing literature as breast neoplasms. Likewise, Primary Care may be in an article as Primary Health Care, and by searching the former, you could miss articles that use the latter. To avoid leaving out relevant articles, use all of the possible terms for your concept:
"breast cancer" OR "breast neoplasms"
"primary care" OR "primary health care"
Alternatively, you can search using subject headings. All databases have a list of controlled vocabulary words that seek to apply a single term to a single concept. When you use subject headings, you do not have to brainstorm all of the possible synonyms for your search term, because the database does that for you. When you enter a serach term, CINAHL and Ovid are set up to automatically suggest subject headings. For instance if you search breast cancer, CINAHL will show you a list of subject headings, of which breast neoplasms is the first result. Try searching with subject headings and see how your results differ from searching with just keywords.
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Modifying an Unsuccessful Search
If you aren't happy with the list of articles your search brings back, here are some ways you might think about changing your search.
1. Too many articles / Articles aren't on topic
2. Too few articles
Photo by Anant Nath Sharma, used with permission under a Creative Commons license
Limits vs Exclusion Criteria
Limits = these are part of your database search, and are set as options in the database itself. They are usually things like article publication dates (e.g. articles published in the last 5 years), language the article is written in, or age of the subjects in the study.
In Ovid, look for the button that says "Additional Limits."
In CINAHL, look for all the check boxes and menus on the search screen or the section that looks like this on the page with the articles from your search.
Exclusion Criteria = these are the reasons you give for not including a study in your literature review. They tend to be things that are not easy to include as a search word and that the database can't select on its own (limits). As an example, for the breast cancer fatigue topic, one of the exclusion criteria will be studies that looked at patients who were still undergoing treatment.