Supplementing the National Early Warning Score (NEWS2) for anticipating early deterioration among patients with COVID-19 infection

Importance: An early minimally symptomatic phase is often followed by deterioration in patients with COVID-19 infection. This study shows that the addition of age and a minimal set of common blood tests taken in patients on admission to hospital significantly improves the National Early Warning Score (NEWS2) for risk-stratification of severe COVID disease. Objective: To supplement the NEWS2 score with a small number of easily obtained additional demographic, physiological and blood variables indicative of severity of COVID-19 infection. Design: Retrospective observational cohort with internal and temporal held-out external validation. Setting: Acute secondary care. Participants: 708 patients admitted to an acute multi-site UK NHS hospital with confirmed COVID-19 disease from 1st March to 5th April 2020. Intervention: Not applicable. Main outcome and measures: The primary outcome was patient status at 14 days after symptom onset categorised as severe disease (WHO-COVID-19 Outcomes Scales 6-8: i.e. transferred to intensive care unit or death). 218 of the 708 patients reached the primary end point. A range of physiological and blood biomarkers as well age, gender, ethnicity and comorbidities (hypertension, diabetes, heart, respiratory and kidney diseases) were assessed for their association with the primary outcome. Results: NEWS2 total score on admission was a weak predictor for severity of COVID-19 infection at 14 days (internally validated AUC = 0.628). The addition of age and common blood tests (CRP, neutrophil count, estimated GFR and albumin) provided substantial improvements to a risk stratification model but performance was still only moderate (AUC = 0.75). Common comorbidities hypertension, diabetes, heart, respiratory and kidney diseases have minor additional predictive value. Conclusions and relevance: Adding age and a minimal set of common blood parameters to NEWS2 improves the risk stratification of patients likely to develop severe COVID-19 outcomes. The addition of a few common parameters is likely to be much easier to implement in a short time-scale than a novel risk-scoring system.