External validation of the ICU-CARB score to predict carbapenem-resistant gram-negative bacteria carriage in critically ill patients upon ICU admission: a multicenter analysis

Background Recognition of carbapenem-resistant gram-negative bacteria (CR-GNB) carriage is frequently delayed, which increases the risk of subsequent infection and transmission. Previously, we developed a scoring system to identify CR-GNB carriage upon intensive care unit (ICU) admission. Although the ICU-CARB score showed satisfactory performance, it has not been externally validated. In this study, therefore, we externally validated the ICU-CARB score. Methods In the previous article, we introduced a risk-scoring system that incorporated seven key variables: neurological disease, high-risk department history, length of stay >= 14 days, ICU history, invasive mechanical ventilation, gastrointestinal tube placement, and carbapenem usage. To externally validate the ICU-CARB score, we conducted a study involving patients admitted to the ICUs of four tertiary hospitals between January 2021 and December 2023. Patients from three hospitals were grouped into Cohort I (n = 815) and those from the fourth hospital into Cohort II (n = 1602). Model calibration, discrimination, and performance were then assessed. Results A total of 2417 patients were included, among which 289 (12%) carried CR-GNB upon ICU admission. Neurological disease, high-risk department history and length of stay >= 14 days were still 3 most important contributing factors in the scoring system. The ICU-CARB score exhibited high calibration, with an area under the receiver operating characteristic curve of 0.825 (95% confidence interval [CI], 0.778-0.873) for Cohort I and 0.823 (95% CI, 0.791-0.855) for Cohort II. The ICU-CARB score showed a highly positive association with CR-GNB carriage in both cohort I (C = 0.315; P < 0.001) and Cohort II (C = 0.381; P < 0.001). Conclusions Despite differences in patient population characteristics, the ICU-CARB score for CR-GNB carriage upon ICU admission exhibited good discrimination in external validation, supporting its potential generalizability to other ICU settings.