How to read a paper: The Medline database
Authors: T. Greenhalgh
Journal: BMJ (1997)

In 1928, in his introduction to Sceptical Essays, Bertrand Russell wrote: "The extent to which beliefs are based on evidence is very much less than believers suppose."Medical beliefs, and the clinical practices that are based on them, are a case in point.Debate continues as to whether scientific evidence alone is sufficient to guide medical decision making, but few doctors would dispute that finding and understanding relevant research based evidence is increasingly necessary in clinical practice.This article is the first in a series that introduces the non-expert to searching the medical literature and assessing the value of medical articles. The Medline databaseOver 10 million medical articles exist on library shelves.About a third are indexed in the huge Medline database, compiled by the National Library of Medicine of the United States.The Medline database is exactly the same, whichever company is selling it, but the commands differ according to the software.Vendors of Medline online and on CD ROM include Ovid Technologies (ovid) and Silver Platter Information (WinSPIRS).Articles can be traced in two ways: by any word listed on the database, including words in the title, abstract, authors' names, and the institution where the research was done; and by a restricted thesaurus of medical titles, known as medical subject heading (MeSH) terms.To illustrate how Medline works, I have worked through some common problems in searching.The scenarios have been drawn up using ovid software.Problem 1: You are trying to find a known paper Solution: Search the database by field suffix (title, author, journal, institution, etc) or by textwords.First, get into the part of the database which covers the approximate year of the paper's publication.If you are already in the main Medline menu, select "database" (Alt-B).If you know the approximate title of the paper and perhaps the journal where it was published, you can use the title and journal search keys or (this is quicker) the .tiand .jnfield suffixes.The box shows some other useful field suffixes.Thus, to find a paper called something like "Confidentiality and patients' casenotes," which you remember seeing in the British Journal of General Practice a couple of years ago, 1 type the following sequence:1 confidentiality.ti 2 british journal of general practice.jn3 1 and 2 You could do all this in one step:1 confidentiality.tiand british journal of general practice.jnThis step illustrates the use of the boolean operator "and"; it will give you articles common to both sets.Using "or" will simply add the two sets together.Note that since 1988 the British Medical Journal is abbreviated BMJ in ovid software, and Journal of the American Medical Association is JAMA.Other useful field suffixes to try when searching for a known article are author (using the syntax haines-ap.au),institution (for example, manchester.in), or title (for example, evidence-based medicine.ti). Summary pointsNot all medical articles are indexed on Medline, and many that are have been misclassified Searching by textword can supplement a search by MeSH headingsTo increase the sensitivity of a search, use the "explode" command and avoid using subheadings Scan titles on screen rather than relying on the software to find the most valid or relevant ones Useful search field suffixes (ovid)