Background: Little is known about why surrogate decision makers for patients with advanced illness often have overly optimistic expectations about prognosis.
Objective: To determine how surrogates interpret prognostic statements and to explore factors influencing surrogates' interpretations of grim prognostic information.
Design: Multicenter, mixed-methods study.
Setting: Intensive care units of 3 hospitals in San Francisco, California.
Participants: 80 surrogates of critically ill patients.
Measurements: Participants recorded their interpretation of 16 prognostic statements using a standard probability scale. Generalized estimating equations were used to determine whether participants interpreted statements more optimistically as the expressed probability of survival decreased. Fifteen surrogates whose responses exhibited this trend participated in a semistructured interview.
Results: Participants' interpretations of prognostic statements expressing a low risk for death were relatively accurate, but interpretations of statements conveying a high risk for death were more optimistic than the actual meaning (P < 0.001; generalized estimating equation model). Interpretations of the statement "90% chance of surviving" did not differ from the actual meaning, but interpretations of "5% chance of surviving" were more optimistic and showed substantial variability (median, 90% [interquartile range, 90% to 95%; P = 0.11] vs. 15% [interquartile range, 5% to 40%; P < 0.001], respectively). Two main themes from the interviews explained this trend: surrogates' need to register optimism in the face of a poor prognosis and surrogates' belief that patient attributes unknown to the physician would lead to better-than-predicted outcomes.
Limitation: Surrogates' interpretations were elicited in an experimental setting rather than during actual clinician-surrogate conversations.
Conclusion: Inaccurate interpretations of physicians' prognostications by surrogates arise partly from optimistic biases rather than simply from misunderstandings.
Primary funding source: National Heart, Lung, and Blood Institute.