Searching PubMed – How to Build a Search Strategy
1.) Go to the PubMed search page: www.pubmed.gov
2.) Select the “Advanced search” option above the search box.
3.) Use “Search Builder” to enter your subject terms and monitor the results for each step.
Sample search: “What is the relationship between caffeine and cancer?”
First, identify the key terms: “caffeine” and “cancer.”
a.) Enter term #1:
Select field: MeSH Major Topic
(MeSH -- Medical Subject Headings -- is a controlled vocabulary and hierarchy which provides precision in searching by topic.)
Enter term in Search Builder box: cancer
Click: Add to Search Box.
Click: red Preview button.
(The Preview button causes the number of articles retrieved to appear as a set in the Search History section below.)
Click: Clear Button. (Next to Preview button.)
b.) Enter term #2:
Select field: MeSH Major Topic
Enter term: caffeine
Click: Add to Search Box.
Click: red Preview button. (Notice results in the Search History section below.)
Click: Clear Button.
c.) Combine search terms:
Combine the terms caffeine and cancer in the Search Box by entering the set numbers from the Search History with the Boolean operator “and”, e.g. #1 and #2
Click: red Preview button and check results in Search History.
This method may seem cumbersome initially but entering terms individually allows for easy search revision if the results are unsatisfactory.
4.) Searches may also be constructed by searching the MeSH database and sending the selected terms to the Search Box. (See “More Resources” at the bottom of the Advanced Search page.) Use this option for help in selecting terms, to define terms, to select subheadings and to turn off automatic “explosion” of terms.
The advantage to using subheadings is that you can match a subheading to a particular subject: for example “caffeine – adverse effects” or “neoplasms – prevention and control” or “neoplasms – drug therapy.”
“Exploding” a term will include that term as well as all the more specific terms in the hierarchy – in this case “cancer” (general) as well as pancreatic cancer, breast cancer, and all other types of cancer, even those that do not include the words “cancer” or “neoplasms,” such as lymphomas or leukemias. Exploding is automatic but in some circumstances you may choose to turn off this feature.
5.) Use Limits to refine the search.
Begin by reviewing the results. Click the “Search” button to see the citations. (Or scroll down to “Search History” and click on the results of the same search.)
In scanning the results you will notice that many articles refer to mice. The next step will restrict the articles to those concerning humans.
Select “Limits” option above Search Box.
- Under “species,” check the “humans” box.
- Click the “search” box at the bottom of the page.
6.) Use Filters (top of right column) to view review articles or those with free full text. Only one filter may be used at a time. To apply both, use the Limit function and choose the options under “type of article” and “text options.”
A review article differs from a research article. It’s a good place to start your research. “Review articles are an attempt by one or more writers to sum up the current state of the research on a particular topic. Ideally, the writer searches for everything relevant to the topic, and then sorts it all out into a coherent view of the “state of the art” as it now stands.” http://www.lib.utexas.edu/lsl/help/modules/review.html.
Free full text may be available in many ways. Two of the most common are direct access provided by the publisher and access provided through the NIH Public Access or other PubMed programs. If the phrase “free text” appears after the citation, you may use the link to go directly to the text. Otherwise, select the article by clicking on the title, then click on “LinkOut – More Sources” at the end of the record. Select the publisher’s link (usually the first).
Articles not available online may be requested through interlibrary loan.
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