ObjectiveTo generate and validate a predictive score of yeast isolation based on independent risk factors of yeast isolation in intensive care unit patients with peritonitis.DesignRetrospective cohort study to determine independent risk factors of yeast isolation, generation of the score, and validation in a prospective cohort of patients with peritonitis.SettingTertiary-care, university-affiliated hospital.PatientsTwo hundred twenty-one patients with peritonitis hospitalized in a surgical intensive care unit between 1994 and 1999 for the retrospective cohort and 57 patients in the prospective cohort (2000).Measurements and Main ResultsFour independent risk factors of yeast isolation in peritoneal fluid (similar odds ratio) were found in the retrospective cohort: female gender, upper gastrointestinal tract origin of peritonitis, intraoperative cardiovascular failure, and previous antimicrobial therapy at least 48 hrs before the onset of peritonitis. A score based on the number of risk factors was constructed (grade A = zero or one risk factor, grade B = at least two risk factors, grade C = at least three risk factors, and grade D = four risk factors), and validated in the prospective cohort. For a grade C score, sensitivity was 84%, specificity was 50%, positive and negative predictive values were 67% and 72%, respectively, and overall accuracy was 71%.ConclusionsFour independent risk factors of yeast isolation in the peritoneal fluid were identified in critically ill surgical patients with peritonitis. The presence of at least three of these factors (grade C score) was associated with a high rate of yeast detection. This approach could be helpful to initiate early antifungal therapy in this patient population.