Determinants for detection of infection with SARS-CoV-2 Omicron variants of concern in health care workers by rapid antigen tests

IMPORTANCE The rapid genetic evolution of SARS-CoV-2 and in particular the highly contagious Omicron variant of concern (VoC) may pose problems for rapid and accurate diagnosis of infection especially in health care workers. OBJECTIVE Determine the diagnostic accuracy and robustness of two rapid antigen tests compared to the golden standard, PCR-based diagnostics, for detection of infection with different SARS-CoV-2 Omicron VoC sub lineages in health care workers. DESIGN, SETTING, AND PARTICIPANTS The study included 428 health care workers from the University Hospital Munich Rechts der Isar who reported recent onset of COVID-19 associated symptoms or completed routine diagnostic testing from 24th of May to 22nd of September 2022. All participants gave written informed consent to participate in this study and completed a questionnaire on infection-associated symptoms, prior SARS-CoV-2 infections and vaccination status. INTERVENTIONS During the first visit, two nasal swabs were taken to perform two rapid antigen tests and one oropharyngeal swab for PCR-based diagnosis of SARS-CoV-2 infection. A second set of nasal swabs was taken by participants two days later for repeated performance of the two rapid antigen tests. MAIN OUTCOMES AND MEASURES The accuracy for detection of infection with different SARS-CoV-2 Omicron VoCs with two rapid antigen tests (Test I and Test II) was determined and compared to quantitative SARS CoV-2 RNA levels detected by PCR. RESULTS In a side-by-side comparison, we found that Test I detected viral nucleocapsids from Omicron VoC (BA.5.2.3) at higher dilutions compared to Test II. In the study, that included a total of 428 health care workers, Test I and Test II detected PCR-confirmed SARS-CoV-2 infection with different Omicron VoCs (BA.2, BA.4, BA.5) with a sensitivity of 89.4% (95% CI 81.9% - 94.6%) and of 83.7% (95% CI 75.12% - 90.18%), respectively. Increased sensitivity by Test I was also reflected by earlier detection of SARS-CoV-2 infection, and lesser test sensitivity by Test II was compensated for by a repeated test performed two days later. CONCLUSIONS AND RELEVANCE The results from the study demonstrate the usefulness of rapid antigen tests for detection of infection with the SARS-CoV-2 Omicron VoC and reveal an advantage of a lower detection limit for earlier detection of infection in health care workers.