Development and Validation of an Early Warning Model for Hospitalized COVID-19 Patients: A Multi-center Retrospective Cohort Study

Background: Timely identification of deteriorating COVID-19 patients is needed to guide changes in clinical management and admission to intensive care units (ICUs). There is significant concern that widely used early warning scores (EWSs) underestimate illness severity in COVID-19 patients and therefore, we developed an early warning model specifically for COVID-19 patients. Methods: We collected electronic medical record data to extract predictors and used these to fit a random forest model. To simulate the situation in which the model would have been developed after the first COVID-19 ‘wave’ in the Netherlands and implemented during the second wave, we performed a temporal validation by splitting all included patients into groups admitted before and after August 1, 2020. Furthermore, we propose a method for dynamic model updating to retain the model’s predictive performance over time. We evaluated model discrimination and calibration, performed a decision curve analysis, and quantified the importance of predictors using SHapley Additive exPlanations values. Findings: We included 3 514 COVID-19 patient admissions from six Dutch hospitals between February 2020 until May 2021, and included a total of 18 predictors for model fitting. The model showed a higher discriminative performance in terms of partial area under the receiver operating characteristic curve (0.82 [0.80 to 0.84]) compared to the National Early Warning Score (0.72 [0.69 to 0.74]) and the Modified Early Warning Score (0.67 [0.65 to 0.69]), a greater net benefit over a range of clinically relevant model thresholds, and good calibration (intercept=0.03 [-0.09 to 0.14], slope=0.79 [0.73 to 0.86]). Interpretation Thisstudyshowsthepotentialbenefitofmovingfromearlywarningmodelsforthegeneralinpatientpopulationtomodelsforspecificpatientgroups. The COVID-19-specific early warning model is available online at https://github.com/jimmsmit/COVID-19_EWSandweencourageotherstofurther validate this model independently.