ViEWS--Towards a national early warning score for detecting adult inpatient deterioration

Aim of study: To develop a validated, paper-based, aggregate weighted track and trigger system (AWTTS) that could serve as a template for a national early warning score (EWS) for the detection of patient deterioration.

Materials and methods: Using existing knowledge of the relationship between physiological data and adverse clinical outcomes, a thorough review of the literature surrounding EWS and physiology, and a previous detailed analysis of published EWSs, we developed a new paper-based EWS - VitalPAC EWS (ViEWS). We applied ViEWS to a large vital signs database (n=198,755 observation sets) collected from 35,585 consecutive, completed acute medical admissions, and also evaluated the comparative performance of 33 other AWTTSs, for a range of outcomes using the area under the receiver-operating characteristics (AUROC) curve.

Results: The AUROC (95% CI) for ViEWS using in-hospital mortality with 24h of the observation set was 0.888 (0.880-0.895). The AUROCs (95% CI) for the 33 other AWTTSs tested using the same outcome ranged from 0.803 (0.792-0.815) to 0.850 (0.841-0.859). ViEWS performed better than the 33 other AWTTSs for all outcomes tested.

Conclusions: We have developed a simple AWTTS - ViEWS - designed for paper-based application and demonstrated that its performance for predicting mortality (within a range of timescales) is superior to all other published AWTTSs that we tested. We have also developed a tool to provide a relative measure of the number of "triggers" that would be generated at different values of EWS and permits the comparison of the workload generated by different AWTTSs.