Paris (AFP) – It’s the key that opens to door from total lockdown: serologic testing, which will show definitively who has contracted COVID-19 and is in theory safe to return to work. “Everyone’s waiting for serologic testing, the whole world,” said France’s Health Minister Olivier Veran. He said that the global research community was focussing on ways of perfecting the tests, which measure viral antibodies in a person’s blood that signal immunity. Veran said that mass production of the tests could start within weeks. “It’s a huge factor, especially when we’re trying to reduce confinement,” he said. The World Health Organization said that serologic tests were still being developed but were yet to be properly evaluated. Current diagnostic tests, known as RT-PCR, are invasive and use genetic analysis to see if a person is actively infected. Serologic testing, which only requires a drop of blood to conduct, focuses instead on finding virus antibodies, the presence of which indicates that an individual has had COVID-19 and is now likely immune.
“Antibodies are one of the key immune response components. They start to be detectable around a week after initial infection,” said Andrew Preston, a reader in Microbial Pathogenesis at the University of Bath.
There are two types of antibodies associated with the COVID-19 immune response: IgM, which the body produces in the early stages of viral response, and IgG, which arrive later on during infection. The tests being developed can identify both antibodies, key hallmarks of a patient’s auto-immune response to the virus. “Thus there is great interest in the use of an antibody test to indicate immunity against disease for use in the lifting of lockdown restrictions,” said Preston. Antibody testing is so crucial because of the large proportion of people with COVID-19 infections who may not show symptoms but can still pass the virus on to others. Such tests already exist for other illnesses. And once they are perfected for the novel coronavirus the results can be analysed in labs using existing hardware.