Avacta said its AffiDX SARS-CoV-2 antigen test does not work as well as previously thought in detecting the Omicron variant.

Last month, the company said its test had been proven in a small clinical study to detect Omicron. But further laboratory analysis carried out by Avacta “indicates that the sensitivity of the test is reduced at lower viral loads when compared with the sensitivity of the AffiDX test with previous SARS-CoV-2 variants.”

The company noted that the performance of all rapid antigen tests has come under scrutiny in light of the large number of mutations in the Omicron variant, adding that the FDA and other sources have said that the tests “generally will detect the Omicron variant but may have reduced sensitivity.”