KOCHI: While the state has bolstered testing to contain Covid-19, the dependence on antigen tests to rule out infection is rising too. The proportion of antigen tests in daily testing now hovers around 75 per cent. Two months back, it was at 60 per cent. The trend is dangerous and could even be detrimental to the public health in the long run, experts warn.
On Wednesday alone, 52,799 antigen tests were conducted across the state, as against 16,310 RT-PCR tests. That despite the Indian Council of Medical Research (ICMR) having earlier warned that antigen tests are far less sensitive, and hence, more likely to fail to identify positive cases. Asymptomatic patients, who are thus likely to be missed, will go on spreading the infection if the state’s large-scale testing strategy remains the same.
“The high dependence on antigen tests, rather than RT-PCR, directly implies increased chances for Covid positive cases to be missed during testing,” said Dr Anup R Warrier, infectious disease expert.“These missed patients would not be informed of their infection nor would they be placed in quarantine, leading to a very high probability of disease spread among others.”The viral load, which could increase over the next few days in such patients, would result in Covid pneumonia, he said.
“That situation could have been averted by early identification with RT-PCR and subsequent treatment. This is a dangerous scenario, as far as the public health is considered. Identifying people with low viral load is not given importance, as they are less likely to spread the infection. But if they are not identified correctly and quarantined, how can one be sure that their viral loads are not going to be high?” Dr Anup said.
According to ICMR, every negative antigen test result of an asymptomatic patient has to be confirmed with RT-PCR to rule out the infection. In June, ICMR permitted states to carry out rapid antigen tests. Except Tamil Nadu, which did not change its policy of depending on RT-PCR tests, all states are conducting antigen tests.
Unlike earlier, there is no clarity now on whether primary contact screening or confirmatory RT-PCR tests are being conducted in the case of negative antigen tests. However, an official with the health department chose to stress on the management of those who turn positive in antigen testing.
“The strategy may vary from district to district, but we do confirmatory RT-PCR tests on symptomatic patients who test positive in antigen tests. We advise them quarantine for 14 days to prevent the spread of infection. Primary contact lists are identified and they are asked to quarantine themselves,” the official said.
Meanwhile, Monu Varghese, a Kochi-based pulmonologist said the whole testing strategy in the state needs to be revamped. “When the pandemic is peaking, reducing the number of tests is not a logical strategy. We do understand the healthcare system is stretched, but we will remain in this precarious situation for many more months if we let our guard down. Though antigen testing gives quick results, it cannot be relied upon because of its low sensitivity. Along with the antigen tests, the number of RT-PCR tests should also be ramped up in the state,” he said.
