KASARAGOD: Recently, a group of people called for antigen testing as part of a random Covid survey was kept waiting for nearly two hours by the doctors.When the restless people enquired, they were told that the team of doctors had to first go to a Covid First-Line Treatment Centre (CFLTC) and conduct antigen tests on the inmates to free up beds for them.
The government’s new Covid management policy of sending home patients from CFLTCs as soon as they test negative in the antigen test is worrying health workers on the ground.Virologists said antigen tests should be used only to identify Covid positive persons and to confirm community spread, and never to rule out an infection.
“That is because compared to the RT-PCR test, an antigen test is 50 per cent less sensitive to detect the coronavirus. That means if a person tests positive, he/she is positive. But if he/she tests negative, there is a 50 per cent chance of the eprson testing positive later,” said Dr Rajendra Pilankatta, virologist and head of the virology lab at the Central University of Kerala.
The virus
A virus has three components: protein, lipid, and nucleic acid, also called the RNA viral genome. Antigen test looks for the presence of the protein in the swab collected from nose or throat. In RT-PCR or reverse transcription-polymerase chain reaction technique, the presence of the nucleic acid or the RNA is detected. A person is infected by the coronavirus if either the protein or the RNA is detected.“But RT-PCR will detect the nucleic acid even if just four viral particles are present. Compared to an RT-PCR, the antigen test is 50 per cent less sensitive. So a positive is a positive. But that cannot be true if the test is negative, he said.
The worry
Since mid-June, the Department of Health Services has been discharging patients from CFLTCs at the first instance of them testing negative in an antigen test.“What worries me is that patients undergo antigen test on the 10th day of their admission. And if they are negative they are sent home,” said another health inspector of an area where the cases are spiralling now.To be sure, patients discharged from CFLTCs are required to stay in room quarantine for seven days. “At the end of the seventh day, RT-PCR test is conducted before the patient is allowed to mingle with his family and others,” said a health inspector posted in Ernakulam district.But in reality, the RT-PCR test is not conducted on any patients in Kasaragod after they are discharged, said at least four health inspectors in Kasaragod district.
On July 15, when Muhammed Azharuddin, 26, a native of Kumbla panchayat, got out of the Covid hospital after 50 days, he became an example of Kerala’s Covid treatment model. He was admitted to the hospital on May 25 and underwent 13 RT-PCR tests, 12 of them turned positive and he had to stay back in the hospital. Back then, a patient was discharged only if two consecutive samples tested negative.Azharuddin was discharged after his antigen test turned negative just once on July 15. He was asked to stay in quarantine for seven days. But after seven days, no RT-PCR test was conducted, he told TNIE.
Viraemia and viraemic period
In the case of Azharuddin, it was safe because he had gone past the viraemic period, the time when he can infect another person, said virologists and doctors. The presence of viruses in the body or viraemia can be for long periods but the infectivity is between the third day of infection to the 15th day, sometimes it may go up to 20 days, they said. So to discharge a person based on an antigen test on the 10th day is risky, they said. “The risk is higher because an RT-PCR test is not done to confirm the absence of the virus after the seventh day,” said a government doctor.On Wednesday, 105 patients tested negative and were sent home based on antigen tests in Kasaragod district.On the same day, 128 persons tested positive.
Fear and solution
Health officials working on the ground said they were not inclined to recommend antigen tests in many areas because it gave false hope to people that they are not infected. “We want to conduct antigen tests to identify infected persons in communities. But we are scared to recommend the test because those who turn negative are throwing caution to the wind,” said another health inspector. Recently, a health inspector working in Kasaragod and native of Payyannur took an antigen test and also gave his sample for an RT-PCR test. The antigen test turned negative and he went home and mingled with his family for Eid. “That evening, his RT-PCR test turned positive. The family has been quarantined now. We will know if they are infected only after 7 days,” the health inspector said. Dr Pilankatta said on an experimental basis all the samples that had tested negative in antigen test should be subjected to the RT-PCR test.