Design and Performance of a New Severity Score for Intermediate Care

Abstract

Background Application of illness-severity scores in Intermediate Care Units (ImCU) shows conflicting results. The aim of the study is to design a severity-of-illness score for patients admitted to an ImCU.

Methods We performed a retrospective observational study in a single academic medical centre in

Pamplona, Spain. Demographics, past medical history, reasons for admission, physiologi- cal parameters at admission and during the first 24 hours of ImCU stay, laboratory variables

and survival to hospital discharge were recorded. Logistic regression analysis was per- formed to identify variables for mortality prediction.

Results A total of 743 patients were included. The final multivariable model (derivation cohort = 554 patients) contained only 9 variables obtained at admission to the ImCU: previous length of

stay 7 days (6 points), health-care related infection (11), metastatic cancer (9), immunosup- pressive therapy (6), Glasgow comma scale 12 (10), need of non-invasive ventilation (14),

platelets 50000/mcL (9), urea 0.6 g/L (10) and bilirubin 4 mg/dL (9). The ImCU severity score (ImCUSS) is generated by summing the individual point values, and the formula for determining the expected in-hospital mortality risk is: eImCUSS points*0.099 – 4,111 / (1 + eImCUSS points*0.099 – 4,111). The model showed adequate calibration and discrimination. Performance

of ImCUSS (validation cohort = 189 patients) was comparable to that of SAPS II and 3. Hos- mer-Lemeshow goodness-of-fit C test was χ2 8.078 (p=0.326) and the area under receiver

operating curve 0.802. Conclusions ImCUSS, specially designed for intermediate care, is based on easy to obtain variables at admission to ImCU. Additionally, it shows a notable performance in terms of calibration and mortality discrimination.