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.

Keywords: Critical care; ED; Mortality; NEWS; NEWS-L.