Kerala launched extensive COVID-19 rapid antibody testing across districts on Monday, with a plan to do at least 15,000 tests a week among priority groups such as health workers in hospitals, those in home quarantine and vulnerable populations such as those with high social exposure, to check if silent disease transmission is happening in the community.
Several public health experts are sceptical about the value of antibody testing in the community at this stage of the pandemic, when the case graph is set to scale the peak of disease transmission and already there are very evident signs of “imminent” community transmission.
Though Kerala, as many other Sates, had tried to do antibody testing much earlier in the epidemic, in April, the lack of reliable antibody kits had torpedoed that plan.
Clinicians’ role
There are many health officials who now feel that the epidemic has reached a point in the State wherein, public health and epidemiology should take a back seat and that clinicians should take over. Because the crucial questions now facing the State Health administration are more regarding hospital preparedness to handle huge patient volume, clinical protocols and how well equipped the State’s public hospitals are to provide ICU care to patients.
However, conducting the antibody testing amongst the health-care workers in hospitals, both COVID and non-COVID, apart from giving clues regarding the spread of infection, will also help the State identify health personnel who may have already been exposed to the virus and hence can be deployed on the front-line for patient care.
Kerala has procured COVID-19 antibody testing kits manufactured by HLL Lifecare Ltd. for the simultaneous detection of IgG and IgM antibodies through serology (blood tests). Some 10,000 kits have already been supplied to districts and another 40,000 is being procured, the Chief Minister had announced.
Herd immunity
Since the idea of herd immunity has sparked much interest, antibody testing will answer public health questions like the proportion of the population which may have attained immunity through silent, prior exposure to the virus. But researchers are still not sure about the value of these tests, given the uncertainties and limitations of antibody tests.
There are still many unanswered questions whether the antibodies that result from SARS-CoV-2 infection will provide sufficient immunity to prevent re-infection or how long this immunity will last.
It takes at least one to three weeks for a person to develop IgM antibodies in response to SARS-CoV-2 infection. A negative IgM test thus has no value and could leave a person with a false sense of security. But once formed, IgM antibodies could last up to three months in an individual.
PCR tests
The Chief Minister had announced that those who were found IgM positive would be re-tested using PCR tests to confirm the infection. The State might incur unnecessary expenditure in this process.
However, the State government seems to be moving ahead with the plan for antibody testing, hoping that any immunity derived, however much short-lived, may help these people tide over the current crisis.