Hospital mortality prediction for intermediate care patients: Assessing the generalizability of the Intermediate Care Unit Severity Score (IMCUSS)

Abstract Purpose The Intermediate Care Unit Severity Score (IMCUSS) is an easy to calculate predictor of in-hospital death, and the only such tool developed for patients in the intermediate care setting. We sought to examine its external validity. Materials and methods Using data from patients admitted to the intermediate care unit (IMCU) of an urban academic medical center from July to December of 2012, model discrimination and calibration for predicting in-hospital death were assessed using the area under the receiver operating characteristic (AUROC) and the Hosmer-Lemeshow goodness-of-fit chi-squared (HL GOF X 2 ) test, respectively. The standardized mortality ratio (SMR) with 95% confidence intervals (95% CI) was also calculated. Results The cohort included data from 628 unique admissions to the IMCU. Overall hospital mortality was 8.3%. The median IMCUSS was 10 (Interquartile Range: 0–16), with 229 (36%) patients having a score of zero. The AUROC for the IMCUSS was 0.72 (95% CI: 0.64–0.78), the HL GOF X 2  = 30.7 ( P Conclusions The IMCUSS exhibited acceptable discrimination, poor calibration, and underestimated mortality. Other centers should assess the performance of the IMCUSS before adopting its use.