Yorkshire Covid-19 test is paused to beef up its detection of the Omicron variant

The Wetherby-based group said that whilst its AffiDX SARS-CoV-2 antigen lateral flow test is effective at identifying high viral loads of Omicron, further laboratory analysis carried out by the firm indicates that the sensitivity of the test is reduced at lower viral loads when compared with the sensitivity of the test with previous SARS-CoV-2 variants such as Delta.

Before the Omicron outbreak late last year, Avacta said that its coronavirus test was the most sensitive lateral flow test available.

The performance of all rapid antigen tests has come under recent scrutiny in light of the large number of mutations in the Omicron variant of the SARS-CoV-2 virus.

The US Food and Drug Administration, as well as other sources, have indicated that antigen tests generally will detect the Omicron variant, but may have reduced sensitivity.

Avacta's test has been shown to detect the Omicron variant of the SARS-CoV-2 virus in patient samples in a small clinical study.

The firm's lateral flow test contains both a proprietary Affimer reagent and a commercially available antibody.

Avacta's data has shown that the Affimer reagent in the AffiDX test detects the Omicron variant with the same sensitivity as the Delta variant.

The problem is the performance of the antibody, with which the Affimer is paired in the test.

As a result, Avacta has independently taken the decision to pause sales of the test whilst it replaces the antibody to ensure the test's performance with the Omicron variant matches the high performance with previous mutations.

Alastair Smith, chief executive of Avacta Group, said: “The continued high performance of the Affimer reagent in the AffiDX antigen test, despite the large number of mutations in the Omicron variant, is testament to the robustness of our platform technology.

“As a responsible business, we set very high standards for ourselves and our products and have continually kept the performance of the AffiDX antigen test under review as new SARS-CoV-2 variants have arisen.

"Our determination to only provide high quality, high performance diagnostic tests has led us to the correct decision to pause all marketing of the AffiDX lateral flow antigen test. We have, of course, been unable to market the product in the UK since October 2021, as the product continues to await approval under the new CTDA regulatory process."

Dr Smith said Avacta believes Covid-19 testing remains a long-term commercial opportunity.

"We will therefore use the robustness of the Affimer platform, and what we have learned about the SARS-CoV-2 virus, to generate the next generation antigen test that will be as resilient as possible to any future mutations," he added.

“The performance of other marketed SARS-CoV-2 antigen lateral flow tests may well be adversely affected by the Omicron variant.

"This mutant is already the dominant SARS-CoV-2 variant in many countries and may soon be the dominant variant globally. We therefore believe it is essential that similar Omicron sensitivity studies be performed on all SARS-CoV-2 antigen tests and the results communicated to ensure the public can have confidence in the results these tests generate.”