Development and validation of automated computer-aided risk scores to predict in-hospital mortality for emergency medical admissions with COVID-19: A retrospective cohort development and validation study

Abstract

Objectives There are no established mortality risk equations specifically for unplanned emergency medical admissions which include patients with SARS-19 (COVID-19). We aim to develop and validate a computer-aided risk score (CARMc19) for predicting mortality risk by combining COVID-19 status, the first electronically recorded blood test results and the National Early Warning Score (NEWS2). Design Logistic regression model development and validation study. Setting Two acute hospitals (York Hospital - model development data; Scarborough Hospital - external validation data). Participants Adult (aged ≥16 years) medical admissions discharged over a 24-month period with electronic NEWS and blood test results recorded on admission. We used logistic regression modelling to predict the risk of in-hospital mortality using two models: (1) CARMc19-N: Age+sex+NEWS2 including subcomponents+COVID19; (2) CARMc19-NB: CARMc19-N in conjunction with seven blood test results and acute kidney injury score. Model performance was evaluated according to discrimination (c-statistic), calibration (graphically) and clinical usefulness at NEWS2 thresholds of 4+, 5+, 6+. Results The risk of in-hospital mortality following emergency medical admission was similar in development and validation datasets (8.4% vs 8.2%). The c-statistics for predicting mortality for CARMc19-NB is better than CARMc19-N in the validation dataset (CARMc19-NB=0.88 (95% CI 0.86 to 0.90) vs CARMc19-N=0.86 (95% CI 0.83 to 0.88)). Both models had good calibration (CARMc19-NB=1.01 (95% CI 0.88 to 1.14) and CARMc19-N:0.95 (95% CI 0.83 to 1.06)). At all NEWS2 thresholds (4+, 5+, 6+) model, CARMc19-NB had better sensitivity and similar specificity. Conclusions We have developed a validated CARMc19 scores with good performance characteristics for predicting the risk of in-hospital mortality. Since the CARMc19 scores place no additional data collection burden on clinicians, it may now be carefully introduced and evaluated in hospitals with sufficient informatics infrastructure.