The numerical translation of verbal probability expressions by patients and clinicians in the context of peri-operative risk communication.

Shared decision-making is central to the pre-operative consent process and accurate communication of risk is dependent on a clear understanding of numerical information by both the patient and clinician. The risk of an adverse event or complication is often described using verbal probability expressions but how these are interpreted by clinicians and patients in the pre-operative setting has not been studied. We asked patients and clinicians to assign a numerical translation (as a percentage) for seven verbal probability expressions in relation to the probability of a major peri-operative complication occurring. In total, data from 290 patients and 57 clinicians were analysed. There was a wide range in percentages assigned by patients to all verbal probability expressions. Patients assigned a wider range of percentage values to each of the verbal probability expressions and these were all significantly higher than those assigned by clinicians: median (IQR [range]) negligible risk 5% (1-15 [0-100]) vs. 0% (0-0 [0-5]); minimal risk 5% (2-10) [0-100]) vs. 1% (0-1 [0-10]); low risk 10% (3-10 [0-100]) vs. 1% (0-2) [0-10]); standard risk 20% (10-40) [0-100]) vs. 1% (1-5) [0-30]); moderate risk 33% (20-50) [0-100]) vs. 5% (3-10) [0-80]); high risk 70% (30-90 [0-100]) vs. 15% (10-40) [1-75]); and very high risk 90% (50-95 [0-100]) vs. 40% (20-50 [5-100]), respectively (p < 0.005 for all comparisons). There is considerable variation in the numerical translation of verbal probability expressions by both patients and clinicians. This suggests that verbal probability expressions should not be used in isolation as part of doctor-patient discussions regarding peri-operative risk.