Objective: To evaluate the effects of "ego bias" on physicians' prognostic judgments. Ego bias is defined as systematic overestimation of the prognosis of one's own patients compared with the expected outcome of a population of similar patients.
Design: A prospective study of an inception cohort of critically ill patients followed until death or discharge from the hospital.
Patients: Consecutive patients admitted to either an ICU or an intermediate ICU at a teaching hospital during January and February 1987, excluding patients admitted after coronary artery bypass grafting, for elective dialysis, or transferred to the intermediate ICU from another critical care unit. MAIN OUTCOME MEASURES AND COMPARISONS: House officers' and critical care attending physicians' assessments of the likelihood of inhospital survival for each patient, and their assessments of the overall survival rate of ICU and intermediate ICU patients were compared with each other and with actual survival rates.
Results: The attending physicians' predictions for individual patients were significantly lower than their judgments of the overall survival rate, 79.8% vs. 88.0%, p = .0067, suggesting the presence of a "reverse ego bias." The house officers' predictions for individual patients were significantly higher than their judgments of the overall survival rate, 73.5% vs. 68.9%, p = .018, suggesting the presence of ego bias. The magnitude and directions of these differences varied significantly among the attending physicians (F = 4.3, degrees of freedom = 3, p = .0062 by repeated-measures analysis of variance) and the house officers (F = 6.3, degrees of freedom = 5, p = .0001).
Conclusions: The critical care attending physicians exhibited reverse ego bias that was mainly a function of their optimism about the overall survival rate for critically ill patients. The house officers exhibited ego bias that was mainly a function of their pessimism about the overall survival rate for critically ill patients.