Avacta Group plc, the developer of Affimer® biotherapeutics and reagents, has received the first data for its SARS-CoV-2 rapid antigen test from ongoing clinical studies in Europe and the UK.
Avacta says these data show “excellent performance of the test in identifying patients with an infectious viral load and no false positive results.”
The SARS-CoV-2 rapid antigen test has been developed to identify infectious individuals so that they can isolate promptly and reduce the spread of COVID-19.
A recent report from the Liverpool Covid SMART Pilot Study indicates that individuals with COVID-19 infection had a significant chance of infecting their contacts if they had a viral load measured by PCR, called the Ct value (cycle threshold value), of approximately 25 or lower. The Ct value indicates how many PCR cycles are required to amplify the viral RNA so that it can be detected and a lower Ct value indicates a higher viral load.
The initial evaluation of Avacta’s lateral flow rapid antigen test with clinical samples has been carried out at two sites, one in EU and one in the UK using patient samples with viral loads confirmed by PCR. 30 positive samples were tested with Ct values of 26 and below, with half of those in the range 22-26, and the lateral flow test identified 29/30 of these correctly as positive.
This indicates a clinical sensitivity of 96.7% for samples with a Ct value below 26. Importantly, out of a total of 26 negative samples tested with the lateral flow device, the test correctly identified all 26 as negative, giving a clinical specificity of 100%. High specificity is critical for a lateral flow test for mass screening so that large numbers of false positives are not generated which would create a major burden on follow-on testing resources, and result in a significant socio-economic cost of unnecessarily isolating people.
On the basis of these initial data, the company will now progress to a full clinical validation with a larger number of patient samples to CE mark the test for professional use, aiming to bring the test to market in Europe around the end of the first quarter of this year.
Alastair Smith, Chief Executive Officer of Avacta Group, said: “I am delighted with the performance of the test with clinical samples which is extremely encouraging.
“On the basis of these initial clinical studies, the lateral flow test shows very good sensitivity in the infectious range of viral loads including at the lower infectious loads with Ct values of 23-26 which compares very favourably with the data reported in the Liverpool Covid SMART Pilot Study report.
“These data from the first clinical studies will allow us to quickly progress with confidence into the full clinical validation of the test, manufactured at scale, at our clinical trial sites in the UK and the EU. I am confident that these data will accelerate our commercial discussions regarding the roll-out of the test when it is approved for professional use.
“I look forward to updating the market on clinical and commercial progress in due course.”