Predictive value of the National Early Warning Score-Lactate for mortality and the need for critical care among general emergency department patients

Abstract

Study objectives What is the predictive value of the National Early Warning Score–Lactate (NEWS-L) score for mortality and the need for critical care in general emergency department (ED) patients?

Methods In this retrospective cohort study, we enrolled all adult patients who visited the ED of an urban academic tertiary-care university hospital in South Korea over 2 consecutive months. The primary outcome was 2-day mortality. The secondary outcomes were the need for critical care (advanced airway use, vasopressor or inotropic agent use, intensive care unit admission) during an ED stay; 2-day composite outcome (2-day mortality and the need for critical care); 7-day mortality; and in-hospital mortality.

Results During the study period, 4624 adult patients visited the ED. Of these, 87 (1.9%) died within 2 days. In total, 481 patients (10.4%) required critical care during their ED stay. The 2-day composite outcome, 7-day mortality, and in-hospital mortality were 10.9% (503/4624), 2.5% (116/4624), and 3.9% (182/4624), respectively. The NEWS-L demonstrated excellent predictive value for 2-day mortality with an area under the receiver operating characteristic curve (AUROC) of 0.96 (95% confidence interval [CI], 0.94-0.98); this value was better than that of the NEWS alone (AUROC 0.94 [95% CI, 0.91-0.96], P = .002). The AUROC of the NEWS-L for the need for critical care was 0.83 (95% CI, 0.81-0.85); for the 2-day composite outcome, it was 0.84 (95% CI, 0.82-0.86); for 7-day mortality, it was 0.94 (95% CI, 0.92-0.96); and for in-hospital mortality, it was 0.87 (95% CI, 0.85-0.90). Logistic regression results confirmed that the ratio of the NEWS to the initial lactate level was 1:1. Similar results were obtained in the subgroup analyses (disease-infection, disease–vascular and heart, disease-others, and nondisease). The high-risk NEWS-L group (NEWS-L ≥ 7, 9.4% of all patients) had an adjusted odds ratio of 28.67 (12.66-64.92) for 2-day mortality in the logistic regression model adjusted for basic characteristics.

Conclusion The NEWS-L can provide excellent discriminant value for predicting 2-day mortality in general ED patients, and it has the best discriminant value regarding the need for critical care and composite outcomes. The NEWS-L may be helpful in the early identification of at-risk general ED patients.