Performance study of a point-of-care antigen test during the SARS-CoV-2 Delta to Omicron variant transition in the USA

Abstract

IntroductionConcerns have been raised regarding the accuracy of diagnostic antigen testing for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant. We compared the performance of the LumiraDx SARS-CoV-2 Antigen Test between symptomatic participants recruited prospectively during the Delta to Omicron variant transition in the USA.MethodsTwo paired anterior nasal swabs were collected from each participant (adults and children) within 12 days of symptom onset between November 24th, 2021 and February 1st, 2022, during which time Omicron replaced Delta as the dominant variant in the sample population. Swabs were tested by the LumiraDx SARS-CoV-2 Antigen Test and compared using real-time polymerase chain reaction (RT-PCR) reference testing. Reference samples identified as positive were sequenced to identify the SARS-CoV-2 variant. Positive percent agreement (PPA) was calculated, with results stratified by RT-PCR cycle threshold (Ct).ResultsOf the 38 participants for whom LumiraDx SARS-CoV-2 Antigen Test results were available, 36 were confirmed positive by RT-PCR. Overall, PPA of the LumiraDx SARS-CoV-2 Antigen Test was 94.7% (95% confidence interval: 82.3%, 99.4%) and PPA was 100% for samples with a Ct <33. Sufficient viral load for sequencing was present in nine samples (six Delta, three Omicron), all of which returned a positive result using the LumiraDx SARS-CoV-2 Antigen Test. There were no performance differences observed between participants with the Delta and Omicron variants.ConclusionsSARS-CoV-2 differences between Delta and Omicron variant mutations did not affect the performance of the LumiraDx SARS-CoV-2 Antigen Test which detects the nucleocapsid protein antigen. The LumiraDx SARS-CoV-2 Antigen Test can be a useful antigen test to diagnose emerging variants of coronavirus disease 2019.