Development and validation of a clinical risk score to predict SARS-CoV-2 infection in emergency department patients: The CCEDRRN COVID-19 Infection Score (CCIS)

Abstract Objectives To develop and validate a clinical risk score that can accurately quantify an emergency department patient’s probability of SARS-CoV-2 infection without the need for laboratory testing Design Cohort study of participants in the Canadian COVID-19 Emergency Department Rapid Response Network (CCEDRRN) registry. Regression models were fitted to predict a positive SARS-CoV-2 test result using clinical and demographic predictors, as well as an indicator of local SARS-CoV-2 incidence. Setting 32 emergency departments in eight Canadian provinces Participants 27,665 consecutively-enrolled patients who were tested for SARS-CoV-2 in participating emergency departments between March 1-October 30,2020 Main outcome measures Positive SARS-CoV-2 nucleic acid test result within 14 days of an index emergency department encounter for suspected COVID-19 disease Results We derived a 10-item CCEDRRN COVID-19 Infection Score using data from 21,743 patients. This score included variables from history and physical examination, and an indicator of local disease incidence. The score had a c-statistic of 0.838 with excellent calibration. We externally validated the rule in 5,295 patients. The score maintained excellent discrimination and calibration, and had superior performance compared to another previously published risk score. Score cutoffs were identified that can rule-in or rule-out SARS-CoV-2 infection without the need for nucleic acid testing with 97.4 % sensitivity (95% CI 96.4–98..3) and 95.9% specificity (95% CI 95.5-96.0). Conclusions The CCEDRRN COVID-19 Infection Score uses clinical characteristics and publicly available indicators of disease incidence to quantify a patient’s probability of SARS-CoV-2 infection. The score can identify patients at sufficiently high risk of SARS-CoV-2 infection to warrant isolation and empiric therapy prior to test confirmation, while also identifying patients at sufficiently low risk of infection that they may not need testing. Trial registration CCEDRRN is registered at clinicaltrials.gov ( NCT04702945 ). Funding The network is funded by the Canadian Institutes of Health Research (447679), BC Academic Health Science Network Society, BioTalent Canada, Genome BC (COV024; VAC007), Ontario Ministry of Colleges and Universities (C-655-2129), the Saskatchewan Health Research Foundation (5357) and the Fondation CHU de Québec (Octroi #4007). These organizations are not-for-profit, and had no role in study conduct, analysis, or manuscript preparation.