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Prakash, E.S. MBBS, MD
Associate professor of physiology, Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, Georgia; email@example.com.
Three guidelines1–3 widely consulted by U.S. medical schools in preparing questions for in-house examinations and the United States Medical Licensing Examination include about 360 examples of multiple-choice questions that have lead-ins such as Which is the most likely diagnosis or treatment or investigation? But there is not even one question phrased to elicit the least likely possibility among a set of four or five potential possibilities. Why is this the case? The question of what is least likely or least appropriate from among a set of seemingly related possibilities arises frequently in medical practice, and in problem solving in general. Knowledge or understanding of what is least likely or least helpful in a given situation may lead to, for example, not administering a harmful medication, not doing an expensive diagnostic test or an invasive procedure with low diagnostic yield, or double-checking the result of a possibly erroneous lab report or physical finding.
Of course, having double negatives in test questions (such as Which of the following solutions is least dilute? Which of the following possibilities is least unlikely?) can introduce construct-irrelevant variance4 and should be avoided. When used, phrases such as least likely or least appropriate should preferably be printed in boldface type5 and/or underlined, since the goals of testing do not include obscuring what is being asked.
With these clarifying strategies in mind, I recommend that the three guidelines mentioned above be revised to include questions focusing on least likely possibilities, since having and using knowledge of such possibilities constitute an integral aspect of systematic thinking and the practice of evidence-based medicine.
E.S. Prakash, MBBS, MD
© 2012 Association of American Medical Colleges
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