CoVA: An Acuity Score for Outpatient Screening that Predicts Coronavirus Disease 2019 Prognosis

Abstract

Background: We sought to develop an automatable score to predict hospitalization, critical illness, or death for patients at risk for coronavirus disease 2019 (COVID-19) presenting for urgent care.

Methods: We developed the COVID-19 Acuity Score (CoVA) based on a single-center study of adult outpatients seen in respiratory illness clinics or the emergency department. Data were extracted from the Partners Enterprise Data Warehouse, and split into development (n = 9381, 7 March-2 May) and prospective (n = 2205, 3-14 May) cohorts. Outcomes were hospitalization, critical illness (intensive care unit or ventilation), or death within 7 days. Calibration was assessed using the expected-to-observed event ratio (E/O). Discrimination was assessed by area under the receiver operating curve (AUC).

Results: In the prospective cohort, 26.1%, 6.3%, and 0.5% of patients experienced hospitalization, critical illness, or death, respectively. CoVA showed excellent performance in prospective validation for hospitalization (expected-to-observed ratio [E/O]: 1.01; AUC: 0.76), for critical illness (E/O: 1.03; AUC: 0.79), and for death (E/O: 1.63; AUC: 0.93). Among 30 predictors, the top 5 were age, diastolic blood pressure, blood oxygen saturation, COVID-19 testing status, and respiratory rate.

Conclusions: CoVA is a prospectively validated automatable score for the outpatient setting to predict adverse events related to COVID-19 infection.

Keywords: COVID-19; outpatient; prognosis; risk prediction.

Figure 1.

Data flowchart for the development and prospective cohorts.

Figure 2.

A, Distributions of adverse events (AEs) within 7 days after initial outpatient evaluation in the respiratory illness clinical/emergency department, binned by acuity score. Colors from light to dark represent distinct AEs: hospitalization, intensive care unit/mechanical ventilation, or death. B, Cumulative incidence of critical illness or death up to 17 days following initial evaluation, based on initial acuity score. Curves are computed based on cross-validation in the development cohort. C and D, Calibration curves: predicted probability of AEs vs observed rate of AEs. C, Calibration for predicting hospitalization (dashed line for the development cohort; and solid line for the prospective cohort). D, Calibration for predicting critical illness or death (dashed line for the development cohort; and solid line for the prospective cohort). The overall calibration (ratio of expected to number of observed AEs) and calibration slopes are reported in Table 2.