Importance  Misperceptions about prognosis by individuals making decisions for incapacitated critically ill patients (surrogates) are common and often attributed to poor comprehension of medical information.
Objective  To determine the prevalence of and factors related to physician-surrogate discordance about prognosis in intensive care units (ICUs).
Design, Setting, and Participants  Mixed-methods study comprising quantitative surveys and qualitative interviews conducted in 4 ICUs at a major US medical center involving surrogate decision makers and physicians caring for patients at high risk of death from January 4, 2005, to July 10, 2009.
Main Outcomes and Measures  Discordance about prognosis, defined as a difference between a physician’s and a surrogate’s prognostic estimates of at least 20%; misunderstandings by surrogates (defined as any difference between a physician’s prognostic estimate and a surrogate’s best guess of that estimate); differences in belief (any difference between a surrogate’s actual estimate and their best guess of the physician’s estimate).
Results  Two hundred twenty-nine surrogate decision makers (median age, 47 [interquartile range {IQR}, 35-56] years; 68% women) and 99 physicians were involved in the care of 174 critically ill patients (median age, 60 [IQR, 47-74] years; 44% women). Physician-surrogate discordance about prognosis occurred in 122 of 229 instances (53%; 95% CI, 46.8%-59.7%). In 65 instances (28%), discordance was related to both misunderstandings by surrogates and differences in belief about the patient’s prognosis; 38 (17%) were related to misunderstandings by surrogates only; 7 (3%) were related to differences in belief only; and data were missing for 12. Seventy-five patients (43%) died. Surrogates’ prognostic estimates were much more accurate than chance alone, but physicians’ prognostic estimates were statistically significantly more accurate than surrogates’ (C statistic, 0.83 vs 0.74; absolute difference, 0.094; 95% CI, 0.024-0.163; P = .008). Among 71 surrogates interviewed who had beliefs about the prognosis that were more optimistic than that of the physician, the most common reasons for optimism were a need to maintain hope to benefit the patient (n = 34), a belief that the patient had unique strengths unknown to the physician (n = 24), and religious belief (n = 19).
Conclusions and Relevance  Among critically ill patients, discordant expectations about prognosis were common between patients’ physicians and surrogate decision makers and were related to misunderstandings by surrogates about physicians’ assessments of patients’ prognoses and differences in beliefs about patients’ prognoses.