How Age, Outcome Severity, and Scale Influence General Medicine Clinic Patients' Interpretations of Verbal Probability Terms

Published In: Journal of General Internal Medicine, v. 9, no. 5, May 1994, p. 268-271

Posted on RAND.org on December 31, 1993

by Dennis J. Mazur, Jon Merz

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It is becoming fashionable in medicine to provide patients with an estimate of the risk of techniques or procedures to try to elicit patient preferences prior to the therapy or procedure. Very often the physician will provide the patient with a verbal probability (for example, using the word rare to describe risk of death from anesthesia or severe pneumonia following a procedure). This article describes how age, type of scale used, and outcome severity influence patients' interpretations of verbal probability terms. The study was based in a Department of Veteran's Affairs Medical Center, and subjects included 210 patients seen consecutively in a general medicine clinic. Patients were provided with a long or a short form that gave probability estimates of a complication (death from anesthesia, severe pneumonia) occurring. All probabilities were given in steps of 10; the long form ranged from 100 out of 100 to 1 out of 1,000,000, and the short form ranged from 100 out of 100 to 1 out of 1,000. Patients were randomized to the type of scale and complication described. Results indicated that the type of scale as well as the type of complication influenced what people thought rare meant. The investigators concluded that more-quantitative estimates may be needed when information is given to patients about complications from surgical procedures.

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