Antibody, Antigen Tests: Expert advice snubbed
While a key recommendation of experts has been quickly rolling out rapid antigen and antibody tests, this is yet to be translated into action despite RT-PCR labs remaining overburdened.
"We recommended on June 3 that antigen tests be introduced fast, but we have not seen any progress on that front," said Prof Nazrul Islam, virologist and former vice chancellor of BSMMU, who is also a member of the government's national technical advisory committee on Covid-19.
He and other experts talked about the gap between what is recommended and what is being implemented at a webinar yesterday, jointly organised by Health Alliance Bangladesh and Bangladesh Health Watch.
They reiterated the immediate need for rapid antigen tests.
"Antigen tests can be used in emergency departments of hospitals to see if a patient is infected or not," said Dr Be-Nazir Ahmed, former director of disease control at the Directorate General of Health Services (DGHS) and an infectious disease specialist.
"When implementing zoning, we need to test every single house. These tests can be used in addition to the RT-PCR because they are quick."
He described two types of tests that can be used.
"A rapid diagnostic test for antigen, called the immunochromatographic, is a qualitative test that can only see if a person is infected or not, but cannot see how infected the person is. But this can provide support to RT-PCR in these circumstances."
Another is the ELISA test -- a quantitative test that can see how many antigens or antibodies are present in a sample.
"I feel that the government is taking a conservative approach to this. The scope for research should be opened up for whoever wants to do it," said Dr Be-Nazir.
Dr M Shawkat Hassan, director of the department of laboratory medicine at Birdem hospital, said, "We have RT-PCR, antigen and antibody tests in our armament.
"I have ordered Birdem to start antigen tests and I am also trying to procure ELISA test kits.
"For antigen tests, if the result comes out positive, then the RT-PCR should be positive. But if the antigen test is negative, then that coincides with RT-PCR only 75 percent times. But even then, it is useful for situations like hospital emergency departments."
On antibody test, experts said it can be used for surveillance of seroprevalence.
"The initial antibody that develops is called Immunoglobulin(M). This peaks in two weeks. When Ig(M) peaks, Immunoglobulin(G) is produced -- this can stay in a body for a few months to a few years. By detecting antibodies, we can tell if the patient had coronavirus infection," said Prof Nazrul.
He added that antibody tests can be used to decide who needs vaccines and who do not. "Vaccines are going to be costly. Antibody tests can be used to see who is eligible for it," he added.
"These can also be used to see whether the plasma donations being given have the right amount of antibodies needed."
Dr Hassan said, "If someone comes to me six days after symptoms appear, I would prefer a total antibody test for Ig(A), Ig(M) and Ig(G). If 14 days had passed, then I should do two Ig(G) tests.
"Antibody tests use blood, not nasal swabs, so it is also more accurate. The limitation of RT-PCR is that the sensitivity depends on the sample collection, the kind of sample, the kind of media being used for testing."
Dr Be-Nazir thinks antibody and antigen tests should have been brought in long back.
"For example, if we could have popularised these tests in low-income areas like slums then we would be able to see what the infection in those areas are like -- on which we do not have enough data at the moment," he added.
On fees imposed for coronavirus tests, Dr Nazrul said, "For a large part of the population, a Tk 200 fee might be too much."
Sadaf Saaz, founder of EskeGen, a clinical research organisation, moderated the event.