Identifying a more severe emergent COVID-19 variant using Emergency Departments' routinely collected clinical measures.

Objective: To determine whether a clinical scoring system (the mPRIEST score) could be used to identify an emerging coronavirus disease 2019 (COVID-19) variant with increased clinical severity.

Design: Cross sectional study comparing two time periods (Delta and Omicron waves).

Setting: Public Emergency Departments in Northern Sydney Local Health District.

Participants: Patients presenting during August 2021 (Delta wave) and January 2022 (Omicron wave) with confirmed COVID-19. Data on age, gender, temperature, heart rate, systolic blood pressure, respiratory rate, oxygen saturation and mental status were extracted from patients' electronic medical records to assess clinical disease severity at presentation.

Main outcome measures: Modified Pandemic Respiratory Infection Emergency System Triage (mPRIEST) score calculated using routinely collected data.

Results: A sample of 262 records of COVID-19 positive patients presenting during the Delta and initial Omicron waves were reviewed with 205 having COVID-19 as their primary diagnosis. During the Delta wave 48.1% had scores above 4 compared to 35.1% for the Omicron wave (p = 0.03). The median score was also significantly higher for the Delta group (4 vs 3; p = 0.01). Hospitalisations, admissions to ICU and deaths during admission were higher among patients presenting during the Delta wave than among those presenting during the Omicron wave.

Conclusion: The mPRIEST score was significantly higher for patients for whom the predominant circulating variant was Delta than those for whom the predominant circulating variant was Omicron. This finding is consistent with international reporting of severity measured by hospital admission data and demonstrates the score's possible ability to identify an emergent strain with higher morbidity and mortality.