Patients' interpretation of qualitative probability statements
K. K. Woloshin, M. T. Ruffin 4th and D. W. Gorenflo
Department of Family Practice, MidMichigan Regional Medical Center, Midland.
BACKGROUND: Physicians often use qualitative probability statements to
compare treatment options or describe risks of treatment, especially if
exact numerical information is not readily available. OBJECTIVES: To
determine (1) the effect of context, experience, age, gender, race,
occupation, and education on patients' numerical interpretation of
probability terms and (2) patient preferences for information about side
effects (qualitative or numerical). DESIGN: Cross-sectional survey.
SETTING: A university-based family practice in Ann Arbor, Mich.
PARTICIPANTS: Patients 18 years of age and older and parents of patients
younger than 18 years of age seen during January and February 1993 for any
reason except complete physical examination. METHODS: A questionnaire
presented scenarios of minor and major complications related to four
different medical conditions. Participants were asked to estimate how many
people of 100 would have a complication if their physician described the
risk for the complication in each scenario as unlikely. Participants were
then asked whether they preferred receiving information from their
physician about the risk for complications in words or numbers. RESULTS: Of
345 questionnaires distributed, 307 patients (89%) completed them. The
rates assigned to the minor complications were significantly higher than
the rates assigned to the major complications (P = .0001). Participants who
had experienced the described complication reported significantly higher
rates for the minor complications of vaccination and surgery (P = .0001 and
P = .0235, respectively). Education had a significant effect only on the
rates assigned to vaccination complications (P = .0069). Occupation had a
significant effect only on the rates assigned to antibiotic side effects (P
= .0090). CONCLUSIONS: When a physician uses qualitative probability
statements, he or she must be sensitive to the patient's previous
experience with that procedure or medication. Also, if one wants to convey
the same potential rate of occurrence for major and minor side effects,
then one needs to use different words for each.
