As the Delhi government prepares to start conducting rapid antibody tests in hotspots such as Nizamuddin West and Dilshad Garden, The Indian Express speaks to Dr S K Sarin, who heads the panel on COVID-19 preparedness, on the road ahead.
What role will the rapid antibody tests play?
It is a good idea because the test can give us a variety of data that can help us understand the disease and its impact better. The swab test has a sensitivity of 60%. DNA is extracted and a PCR test is run. It is a laborious process but a definite one. Once the virus enters the body, it will make antibodies against the viral antigen. These are IgM, produced in the acute phase, and IgG antibodies, produced when the virus starts clearing. They may take 3-7 days to develop. The test kits will be able to tell us if a person was affected acutely or if he has recovered. If the infection is acute or active, a person will have IgM antibodies; if they have recovered, they will have IgG antibodies. You don’t have to take nasal swabs, a blood test is enough. The kit will help us get an idea about the number of people who have been infected.
What we are still trying to understand is that if you have been infected earlier and have developed IgG antibodies, are you protected against the disease? We will have to wait and see if these people are still vulnerable. It is a good method, especially for those in quarantine. In this test, it will take time to find out whether someone has contracted the disease as antibodies take time to develop. In swab tests, there is no need to wait. There are 40,000 people in quarantine in Delhi presently. Many of them can be asked to go back home if the tests are negative. Right now, people who have been in touch with someone who was infected and have symptoms are hospitalised and tested and those without symptoms are quarantined. The test can also tell us if someone has been infected in the past but remained asymptomatic.
What kind of a picture can this testing give us in hotspots?
Random testing is a good idea for nasal swab tests if there are enough available. For those in quarantine, antibody tests are a good idea. Those who have been in contact with patients or healthcare workers should be the first ones to be tested. The antibody tests can also give us data about how people react to the virus. Have the young made more antibodies? What about the response of the elderly or those suffering from diabetes? Who does not make any antibodies? This will give us a clear picture about the body’s response in different age groups with different comorbidities for COVID-19.
Have we seen anything to indicate that we are at the stage of community spread in Delhi so far?
It is very difficult to assess. The New England Journal has a study from South Korea where asymptomatic patients have been studied. To say we don’t have community spread is not easy. Presently, the number of patients is increasing, but not to the extent which was seen in other countries. Cases so far can be categorised as local transmission. We will have to monitor what happens in the next three-four days. If there isn’t a spike, we might have avoided stage 3 for the time being. That said, we need to be prepared for the worst.
Under these circumstances, should the lockdown be extended?
Lockdown is a concept that has to be ingrained. It has to be voluntary, even if not enforced by the authorities. The one thing Indians have done well is using masks early on when the disease started to spread, even before it was advised. The extension of the lockdown will be beneficial as it will arrest the number of deaths. Every life matters. If the lockdown has to be eased, it should be done in a graded manner in areas that are not hotspots. The hotspots should remain cordoned off.
The CM said that if there are 30,000 cases, Delhi will need 400 ventilators. What is the calculation behind that?
Out of every 100 patients, 20 require hospitalisation. Of these, around 2.3 patients require ventilators and five require admission in ICUs. If we get 1,000 patients who stay for seven days, we will need around 140 ventilators. Some of them will be cured and get discharged.
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