Pointers for making the most of your Medline searches
By Chris Dwyer
In June, the U.S. National Library of Medicine (NLM) announced that it was making medicine's premier electronic database, Medline, available on the Internet free of charge.
Putting the Medline database and its "Grateful Med" literature searching software on the Internet is part of the NLM's strategy to increase access to its resources while saving taxpayer dollars. The move is also expected to expose a new group of physicians and patients to Medline, which contains 9 million abstracts from 4,000 biomedical journals.
For newcomers to Medline, or for physicians who want to search the database more efficiently, here are some tips from ACP Annual Session faculty who regularly speak at Computers in Medical Practice courses:
Pose a question. Paul N. Gorman, FACP, assistant professor of medicine and health informatics at Oregon Health Sciences University, offers the following examples of common clinical questions that arise in a primary care setting:
- Migraine patient with possible depression: Do selective serotonin reuptake inhibitors (SSRIs) help?
- Adolescent with meningitis: Do steroids improve outcome?
- Woman with diabetic retinopathy and new transient ischemic attacks (TIAs): Is aspirin safe?
Translate the question into a search statement. To build your search, select the most important two or three concepts in your question and link them together. The questions in the preceding paragraph, for example, translate into the following Medline searches:
- migraine AND serotonin uptake inhibitors
- glucocorticoids, synthetic AND meningitis
- diabetic retinopathy AND aspirin
Use medical subject heading (MeSH) terms. According to Anna Harbourt, a member of the Grateful Med development team at NLM, physicians should rely on the MeSH terms, also known as index terms, that the NLM uses to describe the content of a journal article.
Most search software, including Grateful Med, automatically attempts to translate your search request into MeSH terms. But a more effective strategy is to type in a keyword then go to the list of MeSH terms provided by the search software and choose one or more relevant terms.
For example, type the words "heart disease" and click on the "Find MeSH/Meta Terms" button at the top of the screen, and you'll get a list of several dozen related—and more specific—search terms. You can click on a term to read its definition and see a map of how it fits into the MeSH hierarchy. After reviewing the list, you can choose the concept that most closely fits the topic of your search (for example, try "heart failure, congestive" instead of "heart disease").
Besides providing access to MeSH terms, Grateful Med allows users to identify one or more MeSH terms as a "major topic." This feature tells the search software to return only citations that are primarily about that topic.
Apply filters. Rose Marie Woodsmall, a medical information specialist at the NLM, suggests you decide whether your question is primarily about therapy, diagnosis, etiology or prognosis before performing a search.
Researchers in medical informatics, led by Ann McKibbon from McMaster University, have identified an all-purpose "methodology filter" or "quality filter" for each of these four areas. For example, by choosing the term "clinical trial" from the "publication types" bar of Grateful Med, you'll get articles that focus on using a specific drug to treat a disease or condition.
These filters can cut a long list of citations down to a handful of more appropriate abstracts:
- For information about a particular therapy, go to the "publication types" pulldown box in Grateful Med and choose clinical trial.
- For information about a diagnosis, type "sensitivity" into the "Search for" box and choose title from the pulldown box to the right.
- For information about etiology/causation, type "risk" into the "Search for" box and choose title from the pulldown box to the right.
- For information about a prognosis, type "cohort studies" into the "Search for" box and choose subject from the pulldown box to the right.
Chris Dwyer is Clinical Information Management Program Associate in ACP's Education Division. He can be reached at email@example.com.
Medline on the Web
- Internet Grateful Med
Free Medline searches from the Internet using the NLM's popular Grateful Med search engine. Version 2.3, released during the summer of 1997, also offers free access to other NLM databases.
Free Medline searches using an experimental interface designed to connect medical Internet sites with Medline abstracts and full-text articles from the articles' original publishers. Unique features include a "find related articles" button, as well as filters that automatically restrict searches to therapy, diagnosis, etiology or prognosis.
- Dr. Felix's Free Medline Page
Detailed list of free and low-cost Medline search tools available on the Internet.
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