Utility of SARS-CoV-2 rapid antigen testing for patient triage in the emergency department: A clinical implementation study in Melbourne, Australia.

Background: Early, rapid detection of SARS-CoV-2 is essential in healthcare settings in order to implement appropriate infection control precautions and rapidly assign patients to care pathways. Rapid testing methods, such as SARS-CoV-2 rapid antigen testing (RAT) may improve patient care, despite a lower sensitivity than real-time PCR (RT-PCR) testing.

Methods: Patients presenting to an Emergency Department (ED) in Melbourne, Australia, were risk-stratified for their likelihood of active COVID-19 infection, and a non-randomised cohort of patients were tested by both Abbott Panbio™ COVID-19 Ag test (RAT) and SARS-CoV-2 RT-PCR. Patients with a positive RAT in the 'At or High Risk' COVID-19 group were moved immediately to a COVID-19 ward rather than waiting for a RT-PCR result. Clinical and laboratory data were assessed to determine test performance characteristics; and length of stay in the ED was compared for the different patient cohorts.

Findings: Analysis of 1762 paired RAT/RT-PCR samples demonstrated an overall sensitivity of 75.5% (206/273; 95% CI: 69·9-80·4) for the Abbott Panbio™ COVID-12 Ag test, with specificity of 100% (1489/1489; 95% CI: 99·8-100). Sensitivity improved with increasing risk for COVID-19 infection, from 72·4% (95% CI: 52·8-87·3) in the 'No Risk' cohort to 100% (95% CI: 29·2-100) in the 'High Risk' group. Time in the ED for the 'At/High Risk' group decreased from 421 minutes (IQR: 281, 525) for those with a positive RAT result to 274 minutes (IQR:140, 425) for those with a negative RAT result, p = 0.02.

Interpretation: The positive predictive value of a positive RAT in this setting was high, allowing more rapid instigation of COVID-19 care pathways and an improvement in patient flow within the ED.

Funding: Royal Melbourne Hospital, Melbourne, Australia.