Analytical sensitivity of six lateral flow antigen test kits for variant strains of SARS-CoV-2

Introduction: The lateral flow antigen test is a useful tool for rapid diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The analytical sensitivity of six lateral flow antigen test kits was compared.Methods: The limit of detection (LoD) and time to positive results were evaluated for six lateral flow tests including ImmunoArrow (R), ESPLINE (R) SARS-CoV-2, QuickNaviTM COVID19 Ag, ImmunoAce (R) SARS-CoV-2, PanbioTM COVID-19 Ag Rapid Test Device, and SARS-CoV-2 Rapid Antigen Test using the heat-inactivated virus. The LoD of ImmunoArrow (R) against the Omicron variants was compared with that against the wild-type using recombinant proteins.Results: ImmunoArrow (R) and ESPLINE (R) showed the lowest LoD. The time to positive results of all tests except for ESPLINE (R) was within 200 s in the evaluation at high dose of antigens (2.5 x 105 TCID50/mL) and 500 s in the evaluation at low dose of antigens (2.5 x 104 TCID50/mL). The LoD of ImmunoArrow (R) against the Omicron variants was the same concentration against the wild-type antigen. Conclusions: ImmunoArrow (R) detected SARS-CoV-2 antigens including the Omicron variants with good sensitivity among the six lateral flow antigen tests. These finding support that it can support the rapid diagnosis of COVID-19 with the good sensitivity.