Development and validation of the quick COVID-19 severity index (qCSI): a prognostic tool for early clinical decompensation

Haimovich, Adrian; Ravindra, Neal G.; Stoytchev, Stoytcho; Young, H. Patrick; PerryWilson, Francis; van Dijk, David; Schulz, Wade L.; Taylor, R. Andrew

Abstract Objective The goal of this study was to develop a prognostic tool of early hospital respiratory failure among emergency department (ED) patients admitted with COVID-19. Methods This was an observational, retrospective cohort study from a nine ED health system in the United States of admitted adult patients with SARS-CoV-2 (COVID-19) and a ≤ 6 L/min oxygen requirement. We sought to predict respiratory failure within 24 hours of admission as defined by oxygen requirement of ≥ 10 L/min, any high-flow device, non-invasive or invasive ventilation, or death. Predictive models were compared to the Elixhauser comorbidity index, quick serial organ failure assessment (qSOFA), and the CURB-65 pneumonia severity score. Results During the study period from March 1 to April 27, 2020, 1,792 patients were admitted with COVID-19, 620 (35%) of whom had respiratory failure in the ED. Of the remaining 1,172 admitted patients, 144 (12.3%) met the composite endpoint within the first 24 hours of hospitalization. Using area under receiver-operating characteristic curves, we compared the performance of a novel bedside scoring system, the quick COVID-19 severity index (qCSI) composed of respiratory rate, oxygen saturation, and oxygen flow rate (mean [95% CI]) (0.81 [0.73-0.89]), a machine- learning model, the COVID-19 severity index (0.76 [0.65-0.86]), to the Elixhauser mortality index (0.61 [0.51-0.70])), CURB-65 (0.50 [0.40-0.60]), and qSOFA (0.59 [0.50-0.68]). A low qCSI score (≤ 3) had a sensitivity of 0.79 [0.65- 0.93] and specificity of 0.78 [0.72-0.83] in predicting respiratory decompensation with a less than 5% risk of outcome in the validation cohort. Conclusions A significant proportion of admitted COVID-19 patients progress to respiratory failure within 24 hours of admission. These events are accurately predicted using bedside respiratory exam findings within a simple scoring system.