The Pediatric Risk of Hospital Admission Score: A Second-Generation Severity-of-Illness Score for Pediatric Emergency Patients

Abstract

Objective. To develop and validate a second-generation severity-of-illness score that is applicable to pediatric emergency patients. The Pediatric Risk of Admission (PRISA) score was developed in a single hospital and was recalibrated and validated in 2, previous, small studies from academic pediatric hospitals. This study was performed to develop and validate a score in a larger sample of diverse hospitals. Methods. Emergency departments (EDs) were block randomly selected as part of a study on ED quality on the basis of 3 care characteristics: annual patient volume (high or low compared with national median), presence or absence of a pediatric emergency medicine subspecialist, and presence or absence of residents. Patients were selected randomly on the basis of daily arrival logs. Medical records were photocopied, and abstracted data included demographic, historical, physiologic, and therapeutic information. The total sample was randomly divided into a 75% development sample and a 25% validation sample. Univariate and multivariate analyses were used to model the risk of mandatory admission, admissions for which preidentified, inpatient medical resources were used. The resulting multiple logistic regression model coefficients were converted to integer scores. Calibration (Hosmer-Lemeshow goodness of fit) and discrimination (area under the ROC curve) were used to measure performance. As a measure of construct validity, proportions of patients in ordered risk intervals were correlated with the outcomes of admission, mandatory admission, and ICU admission. Results. Sixteen EDs enrolled 11664 patients. Mean patient age (±SD) was 6.8 ± 5.8 years, and 53% were male. Nine percent arrived by emergency medical services, and 6.9% were admitted. The most common diagnoses were minor injuries, otitis media, and fever. The multivariate analysis yielded a score with 7 historical variables, 8 physiologic variables, 1 therapy (oxygen) term, and 1 interaction term. Calibration was excellent. In the development sample, 442 mandatory admissions were predicted and 442 were observed (total χ2 = 2.275), and in the validation sample, 136.6 were predicted and 145 were observed (χ2 = 8.575). The area under the receiver operator characteristic curve was 0.82 ± 0.01 (SE) in the development sample and 0.77 ± 0.02 in the validation sample. In ordered predicted risk intervals, the proportion of patients with admissions, mandatory admissions, and ICU admissions increased in a linear manner. Conclusions. The second-generation PRISA II score for pediatric ED patients has been developed and validated in a large sample of diverse hospitals. Performance characteristics indicate that PRISA II will be useful for institutional comparisons, benchmarking, and controlling for severity of illness when enrolling patients in clinical trials.