Background The National Early Warning Score + Lactate (NEWS+L) Score has been previously shown to outperform NEWS alone in prediction of mortality and need for critical care in a small adult ED study. We validated the score in a large patient data set and constructed a model that allows early prediction of the probability of clinical outcomes based on the individual’s NEWS+L Score.

Methods In this retrospective study, we included all adult patients who visited the ED of a single urban academic tertiary-care university hospital in South Korea for five consecutive years (1 January 2015 to 31 December 2019). The initial (<1 hour) NEWS+L Score is routinely recorded electronically at our ED and was abstracted for each visit. The outcomes were hospital death or a composite of hospital death and intensive care unit admission at 24 hours, 48 hours and 72 hours. The data set was randomly split into train and test sets (1:1) for internal validation. The area under the receiver operating characteristic curve (AUROC) value and area under the precision and recall curve (AUPRC) value were evaluated and logistic regression models were used to develop an equation to calculate the predicted probabilities for each of these outcomes according to the NEWS+L Score.

Results After excluding 808 patients (0.5%) from 149 007 patients in total, the study cohort consisted of 148 199 patients. The mean NEWS+L Score was 3.3±3.8. The AUROC value was 0.789~0.813 for the NEWS+L Score with good calibration (calibration-in-the-large=−0.082~0.001, slope=0.964~0.987, Brier Score=0.011~0.065). The AUPRC values of the NEWS+L Score for outcomes were 0.331~0.415. The AUROC and AUPRC values of the NEWS+L Score were greater than those of NEWS alone (AUROC 0.744~0.806 and AUPRC 0.316~0.380 for NEWS). Using the equation, 48 hours hospital mortality rates for NEWS+L Score of 5, 10 and 15 were found to be 1.1%, 3.1% and 8.8%, and for the composite outcome 9.2%, 27.5% and 58.5%, respectively.

Conclusion The NEWS+L Score has acceptable to excellent performance for risk estimation among undifferentiated adult ED patients, and outperforms NEWS alone.