Surrogate decision makers' interpretation of prognostic information: a mixed-methods study.

Surrogate decision makers for patients with advanced critical illness are frequently asked to determine whether use of life support is consistent with a patient’s values and goals. Answering this question requires a clear understanding of not only the patient’s values but also the likely outcomes of treatment. Previous research has shown that prognostic information affects decisions to withhold or withdraw life support (1–3). However, discordance about prognosis between physicians and surrogate decision makers in intensive care units (ICUs) is common (4, 5). Medical commentators have often attributed this discordance to surrogates’ misunderstandings about physicians’ prognostications (4, 5). This is a plausible explanation because physicians use diverse types of language to disclose prognostic information (6), and previous studies have documented wide variation in how laypeople interpret qualitative prognostic statements (7–9). Although these findings have compelled some commentators to advocate for the use of numerical prognostic statements (10), it is uncertain whether numerical risk statements are interpreted more precisely than qualitative probability statements. It is also possible that the prevalent physician–surrogate discordance about prognosis is due to other factors. For example, recent evidence suggests that different explanatory models of illness may contribute to discordance about prognosis (3, 11–13). Another possibility is that psychological processes, such as optimism or denial, may contribute. Recent studies assessing the expectations of participants in phase 1 and 2 clinical cancer trials for therapeutic benefit have demonstrated substantial overestimation of the likelihood of positive clinical response, which was driven in part by a need to “register optimism” (14, 15). The possibility that similar processes may be at play in the context of surrogate decision making about clinical care has not been systematically examined. We therefore conducted this study to determine how surrogates interpret prognostic statements and to explore what factors influence surrogates’ interpretations of grim prognostications by physicians.