The National Early Warning Score (NEWS) for outcome prediction in emergency department patients with community-acquired pneumonia: results from a 6-year prospective cohort study

Objective: To investigate the accuracy of the National Early Warning Score (NEWS) to predict mortality and adverse clinical outcomes for patients with community-acquired pneumonia (CAP) compared to standard risk scores such as the pneumonia severity index (PSI) and CURB-65. Design: Secondary analysis of patients included in a previous randomised-controlled trial with a median follow-up of 6.1 years. Settings: Patients with CAP included on admission to the emergency departments (ED) of 6 tertiary care hospitals in Switzerland. Participants: A total of 925 patients with confirmed CAP were included. NEWS, PSI and CURB-65 scores were calculated on admission to the ED based on admission data. Main outcome measure: Our primary outcome was all-cause mortality within 6 years of follow-up. Secondary outcomes were adverse clinical outcome defined as intensive care unit (ICU) admission, empyema and unplanned hospital readmission all occurring within 30 days after admission. We used regression models to study associations of baseline risk scores and outcomes with the area under the receiver operating curve (AUC) as a measure of discrimination. Results: 6-year overall mortality was 45.1% (n=417) with a stepwise increase with higher NEWS categories. For 30 day and 6-year mortality prediction, NEWS showed only low discrimination (AUC 0.65 and 0.60) inferior compared to PSI and CURB-65. For prediction of ICU admission, NEWS showed moderate discrimination (AUC 0.73) and improved the prognostic accuracy of a regression model, including PSI (AUC from 0.66 to 0.74, p=0.001) and CURB-65 (AUC from 0.64 to 0.73, p=0.015). NEWS was also superior to PSI and CURB-65 for prediction of empyema, but did not well predict rehospitalisation. Conclusions: NEWS provides additional prognostic information with regard to risk of ICU admission and complications and thereby improves traditional clinical-risk scores in the management of patients with CAP in the ED setting.