10 Aug 2021
COVID-19 serological test evaluation
Peer review: Open Forum Infectious Diseases
Funding: Victorian Department of Health and the Australian Government Department of Health.
Doherty Institute researchers have evaluated six commercial SARS-CoV-2 serological assays to understand their reliability and role in detecting natural infection or vaccine-induced antibodies.
After infection with a virus, the majority pf people will develop an immune response which includes producing antibodies to the infecting virus.
These antibodies are detectable in a patient’s blood using serological tests, and identify people who have been infected with the virus, or vaccinated against the virus, and can be an indication of protection.
Royal Melbourne Hospital’s Suellen Nicholson, Head of the Infectious Diseases Serology Laboratory at the Doherty Institute said reliable COVID-19 serosurveillance is important for guiding the pandemic response.
“At the individual level, serology can provide a tool for resolving the diagnosis for patients with infections not confirmed by the gold-standard, commonly used PCR test,” Ms Nicholson said.
“At the population level, it provides policy-makers with an assessment of the overall impact of the pandemic and vaccination efficacy.”
Published in Open Forum Infectious Diseases, The team led by Ms Nicholson, tested six commercially-available serology assays using a cohort of PCR-positive samples, samples of pre-pandemic sera and samples from people that could possibly cross-react in serology testing.
“We specifically looked at responses to different antibodies including binding or non-neutralising antibodies. The presence of these antibodies provides serological evidence consistent with either vaccination or SARS-CoV-2 infection and may indicate whether infection or vaccination was recent or not. However they won’t tell you whether you’re potentially protected or not,” she explained.
“In addition we compared neutralising antibodies which block entry of the virus into your cells, thereby providing protection. However the level of neutralising antibody required for protection from the virus is still uncertain.”
Included in the comparisons was a gold-standard micro neutralisation assay from Professor Kanta Subbarao’s laboratory at the Doherty Institute.
“Micro neutralisation assay is considered the gold standard for detecting neutralising antibodies that indicates a level of protection. These assays take five days to complete, requires technical expertise as is labour intensive,” Ms Nicholson said.
“So that’s one of the main strengths of this study is that people can compare these easier and quicker to perform serological assays with the gold standard micro neutralisation test.”
The results showed that all the assays tested were good enough to be used, additionally, there is a better understanding of the strengths and weaknesses of each one.
“We have looked at the sensitivity of these tests, so their ability to detect a true positive and the specificity which is the ability to detect a true negative. It’s important to understand the performance characteristics of the assay,” she said.