Performance of three rapid antigen tests against the SARS-CoV-2 Omicron variant

Abstract

Rapid antigen detection tests (RADTs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are now in widespread use in the United States. RADTs play an important role in maintaining an open society but require periodic reassessment to ensure test performance remains intact as the virus evolves. The nucleocapsid (N) protein is the target for the majority of RADTs and the SARS-CoV-2 Omicron variant has several N protein mutations that are previously uncharacterized. We sought to assess the impact of these mutations by testing 30 Omicron variant samples across a wide range of viral loads on three widely used RADTs: the iHealth COVID-19 Antigen Rapid Test, the ACON Laboratories FlowFlex COVID-19 Antigen Home Test, and the Abbott BinaxNOW COVID-19 Antigen Card, using 30 Delta variant samples as a comparator. We found no change in the analytic sensitivity of all three RADTs for detection of Omicron versus Delta, but noted differences in performance between assays. No RADT was able to detect samples with a cycle threshold (Ct) value of ≥27.5 for the envelope gene target on the Roche cobas RT-PCR assay. Epidemiologic studies are necessary to correlate these findings with their real-world performance.

Rapid quantitation of SARS-CoV-2 antibodies in clinical samples with an electrochemical sensor

“…Lateral flow immunoassays (LFIAs) are more rapid, but they produce less reliable results and are qualitative rather than quantitative ( Dou et al, 2015 ; Flower et al, 2020 ; Michel et al, 2020 ). Rapid antigen detection tests (RADTs) now widely used in the United States for detection of viral proteins could be adapted for detection of antibodies, but they have low sensitivity ( Kanjilal et al 2022a , 2022b ). Another option would be use of chemiluminescent enzyme immunoassays (CLIAs) (Abbott and Roche Elecsys), however, they are costly, lack scalability, and need intricate analytical platforms ( Tan et al, 2021 ).…”

Comparative performance of COVID-19 Test Methods in Healthcare Workers during the Omicron Wave

“…Early studies during the omicron wave show varied sensitivity between Ag-RDT brands 5 , with some such as the BinaxNOW showing maintained sensitivity of around 65% 6 . Other brands such as iHealth have shown similar sensitivity in detecting delta and omicron variants in the laboratory but have not been as widely validated in epidemiologic studies during the delta and omicron waves 7 .…”

“…Other brands such as iHealth have shown similar sensitivity in detecting delta and omicron variants in the laboratory but have not been as widely validated in epidemiologic studies during the delta and omicron waves 7 .…”

Next-Generation Rapid and Ultrasensitive Lateral Flow Immunoassay for Detection of SARS-CoV-2 Variants

“…Lateral flow immunoassay (LFIA) is a qualitative POCT diagnosis method that uses antibody–antigen interactions; it could detect SARS-CoV-2 antigen within 15 min in urine, saliva, sweat, serum, plasma, whole blood, and other fluids. , Considering the number and structural characteristics of proteins, the target proteins for LFIA detection are usually the S and N proteins. − SARS-CoV-2 is characterized by frequent mutations, whereas, compared with S proteins, N proteins are not prone to mutation with the renewal of virulent strains. , Therefore, the stability of N protein makes LFIA highly reliable in detecting SARS-CoV-2 and its variants . However, the sensitivity of existing commercial LFIA strips for SARS-CoV-2 detection is inadequate, with the limit of detection (LOD) estimated to be about 0.1–10 ng/mL (N protein), which is approximately equal to the cycle threshold (Ct) level of about 27–29 of q-PCR. − The lack of sensitivity of LFIA resulted in an extremely high occurrence of “false negatives”. − …”