1 November 2001
NEW YORK -- The most important part about searching the medical literature is framing the right question. And nowadays the question is framed and the literature is critically appraised within the structure of evidence-based medicine.
That's the advice of helen-ann brown, MLS, MS, Librarian on the Information Services Team, Weill Cornell Medical Library, New York NY, who teaches medical students, residents, and faculty how to research the literature. (brown spells her name in lower case.)
Evidence-based medicine asks 2 questions about the literature, said brown:
"You look at the elements of the scenario and formulate background and foreground questions," says brown.
Answers to background questions are found in books, literature from professional organizations or journal review articles. "MEDLINE would not be your first choice for background questions," said brown.
Textbooks such as Harrison's Principles of Internal Medicine are available in print and online versions. MD Consult is a commercial resource of about forty online versions of specialty textbooks. One free on-line textbook for background information, which is being marketed heavily, is Emedicine .
For links to free peer-reviewed textbooks on the Internet, see MedicalStudent.com , MEDLINEPlus from the National Library of Medicine, or Medical Matrix .
Professional organizations. brown also suggests going to a professional organization's web site. A list can be found on the Virtual Hospital .
Search engines. To search the Internet, brown recommends Google as a single search engine and Ixquick as a metasearch engine.
Ixquick eliminates duplicates, and awards each site one star for each search engine that placed it in its top ten for your search, clearly indicating the quality of the result.
Review articles published in journals, such as the New England Journal of Medicine , are another good source to answer background questions. "I would not make a habit of going to the New England Journal of Medicine first," said brown. "I would look at everything that was available." To retrieve review articles, most online searching systems like PubMed , Ovid or SilverPlatter will let you limit your search to review articles.
When you finish PICO, "You have the basic elements and you can put them into an online literature searching system," said brown.
You can search PubMed , Ovid, Silver Platter, Medscape , SumSearch or others. PubMed and SumSearch are available to all with an internet connection at no charge.
Cochrane Library. "For foreground questions especially about therapy, people turn now to the Cochrane Library , for a systematic review of the literature," said brown. "At the moment they are the most sought-after kind of literature to answer a foreground question," she said. The reviews are written in a systematic way, indicating search strategy, kinds of studies to be included, kinds of studies to be excluded and how conclusions are reached. Cochrane systematic reviews are indexed in PubMed, but the complete review is available on CD or through online searching systems, such as Ovid Technologies .
PubMed , especially the Clinical Queries section, is another place to find answers to foreground questions, recommends brown. Clinical Queries is a choice under PubMed Services, located on the blue bar on the left side of the web site. The articles in Clinical Queries have been pre-filtered in an evidence-based way, so you retrieve randomized controlled studies, double-blind studies, or placebo-controlled studies to answer therapy questions.
For this example, on the Clinical Queries page you would leave the default buttons selected at "therapy" and "specificity," and type in the search box "weight reduction AND hypertension" or "diet plans AND blood pressure", brown explained. (PubMed requires the searching operators, AND and OR, be entered in capital letters.)
McKibbon, Ann. PDQ: Evidence-Based Principles and Practice, Hamilton, Ontario: BC Decker, Inc., 1999.
Greenhalgh, Trisha. How to Read a Paper: The Basics of Evidence Based Medicine. London: BMJ, 2001.
Guyatt, Gordon. User's Guides to the Medical Literature: A Manual for Evidence-based Clinical Practice, Chicago, IL: AMA Press 2002
Evidence-based Medicine Resource Center at the New York Academy of Medicine
Health Information Research Unit-McMaster University
Duke University EBM Subject Guide
Thomas Jefferson University EBM Tutorials