PubMed: Dana Medical Library

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Advanced Search Techniques

Importance of the Initial Question
How PubMed Translates a Search
Identify Additional Search Terms
Limits
Related Articles
Combine Search Queries

Importance of the Initial Question

A good question is the backbone of a good search. Focused questions on specific topics result in the best PubMed searches. Questions that cover a broad subject area will need to be focused in other ways. Limiting to review articles, or to Clinical Queries, or to articles from specific journals are some of the ways to focus a broad topic.

If the question is truly a request for an overview of a subject, perhaps PubMed is not the best database to use. Databases that provide background information include online textbooks, FirstConsult, UpToDate, and other databases available from the Dana Medical Library.

How PubMed Translates a Search

PubMed records include author, title and journal information, but they also include MeSH terms (Medical Subject Headings) selected from a list of terms maintained by the U.S. National Library of Medicine. MeSH terminology provides a consistent way to retrieve information when different words or phrases are used for the same concept. PubMed translates the words a user types in into MeSH Terms. As a backup measure, PubMed also includes the words the user typed in and calls them text words. Click on the Details tab to see how PubMed translates a search for articles on the use of NSAIDS (non-steroidal anti-inflammatory drugs) and the prevention of strokes.

Check the Details tab each time you perform a search in PubMed, as it will identify misspellings, dual meanings, and unintended uses of terms. For example, if you wish to investigate the inheritance patterns of a given disease, you will quickly learn that the word "inheritance" maps to the MeSH term "wills", a meaning far from what you'd intended! Using the term "genetics" will yield much more relevant results.

Identify Additional Search Terms

Often the initial search strategy used in PubMed does not target exactly the right articles. One way to modify a search is to look at the MeSH Terms added to those records which were on target, and then type in those terms in a subsequent search. For example in the search above, you might use Cerebrovascular Accident instead of Stroke, especially if you look at a few of the records and find that some of them are about Stroke Volume in the heart and have nothing to do with the brain.

The relevant PubMed record displayed in the search above also showed Practice Guidelines as a MeSH Term. If that's really what you're looking for, add that to the search as well. Thus the next attempt at that search would be for Cerebrovascular Accident prevention nsaids Practice Guidelines.

Limits

Very often PubMed brings up far more hits than you have time or energy to wade through. By applying a few limits, you can reduce this number to a smaller and more focused set of results.

Knowing PubMed contains citations to articles in non-English languages as well as to non-human studies, applying limits for English language and Humans is the best approach for any search on a clinical topic. Limiting to Review articles will further reduce the numbers. Finally, limiting the search to Core Clinical Journals will limit your results to citations from highly regarded, readily available publications, all of which Dana Medical Library subscribes to in print or electronically.

Other available limits include topic, gender, and age group. It is possible to limit by publication year, although this is generally not necessary since the most recently added citations will be displayed first.

The limits you selected will remain in force until you un-check the Limits box, go into the Limits tab to change your selections, or close out PubMed.

Each citation brought up in PubMed will have a Related Articles link on the right margin. Clicking on this link will launch a search for articles on the same or similar topics. Results will be displayed in relevancy-ranked order rather than in reverse chronological order, with the original article listed first. This is an excellent tool to find similar articles to the one good article you started out with and does not require knowledge of MeSH Terms or use of the more sophisticated PubMed tools.

Combine Search Queries

PubMed is set up to allow you to type in your search all at once. But sometimes it's helpful to combine only two terms, then add a third and evaluate the result. You can do several versions of the same search and compare the results.

The History tab provides a way to combine searches, backtrack to a previous search, and remind yourself of what you've already searched.

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