Tracking the National Early Warning Score 2 from Prehospital Care to the Emergency Department: A Prospective, Ambulance-Based, Observational Study

<b>Aim of the study:</b> To assess the prognostic ability of the National Early Warning Score 2 (NEWS2) at three time points of care -at the emergency scene (NEWS2-1), just before starting the transfer by ambulance to the hospital (NEWS2- 2), and at the hospital triage box (NEWS2-3)- to estimate in-hospital mortality after two days since the index event. <b>Methods</b>: Prospective, multicenter, ambulance-based, cohort ongoing study in adults (&gt;18 years) consecutively attended by advanced life support (ALS) and evacuated with high-priority to the emergency departments (ED) between October 2018 and May 2021. Vital sign measures were used to calculate the NEWS2 score at each time point, then this score was entered in a logistic regression model as the single predictor. Two outcomes were considered: first, all-cause mortality of the patients within 2 days of presentation to EMS, and second, unplanned ICU admission. The calibration and scores comparison was performed by representing the predicted vs the observed risk curves according to NEWS score value. <b>Results:</b> 4943 patients were enrolled. Median age was 69 years (interquartile range 53- 81). The NEWS2-3 presented the better performance for all-cause two-day in-hospital mortality with an AUC of 0.941 (95% CI: 0.917-0.964), showing statistical differences with both the NEWS2-1 (0.872 (95% CI: 0.833-0.911); p &lt; 0.003) and with the NEWS2- 2 (0.895 (95% CI: 0.866-0.925; p &lt; 0.05). The calibration and scores comparison results showed that the NEWS2-3 was the best predictive score followed by the NEWS2-2 and the NEWS2-1, respectively. <b>Conclusions:</b> The NEWS2 has an excellent predictive performance. The score showed a very consistent response over time with the difference between “at the emergency scene” and “pre-evacuation” presenting the sharpest change with decreased threshold values, thus displaying a drop in the risk of acute clinical impairment.

**研究目的**：评估国家早期预警评分2（National Early Warning Score 2，NEWS2）在三个照护时间节点——急诊现场（NEWS2-1）、救护车转运入院前（NEWS2-2）及医院分诊台（NEWS2-3）——对指数事件发生后2天内院内死亡的预测能力。**方法**：本研究为前瞻性、多中心、基于救护车的队列研究，目前仍在进行中，纳入2018年10月至2021年5月期间，连续接受高级生命支持（Advanced Life Support，ALS）并以高优先级转运至急诊科（Emergency Department，ED）的18岁及以上成年患者。研究人员于各时间点通过生命体征测量值计算NEWS2评分，并将该评分作为单一预测因子纳入逻辑回归模型。本研究设定两类结局指标：其一为患者就诊于急诊医疗服务机构（Emergency Medical Services，EMS）后2天内的全因死亡率；其二为非计划重症监护病房（Intensive Care Unit，ICU）入住率。校准分析与评分比较通过依据NEWS评分值绘制预测风险与观察风险曲线完成。**结果**：本研究共纳入4943例患者，中位年龄为69岁（四分位间距53~81岁）。NEWS2-3对2天院内全因死亡的预测性能最优，受试者工作特征曲线下面积（Area Under the Receiver Operating Characteristic Curve，AUC）为0.941（95%置信区间：0.917~0.964），其预测性能显著优于NEWS2-1（AUC=0.872，95%CI：0.833~0.911；p<0.003）与NEWS2-2（AUC=0.895，95%CI：0.866~0.925；p<0.05）。校准分析与评分比较结果显示，NEWS2-3的预测效能最优，其次为NEWS2-2，最后为NEWS2-1。**结论**：NEWS2具有优异的预测性能，其预测效能随时间推移表现出高度一致性；“急诊现场”与“转运前”两个时间点的评分差异最为显著，阈值有所降低，提示急性临床不良事件的风险有所下降。