Of the 51,994 tests carried out on August 3 in Maharashtra, 30,593 (59%) were rapid antigen tests, while 20,775 (40%) were performed using the molecular RT-PCR test. The remaining 1% tests were done using CBNAAT and TrueNat machines, originally used for tuberculosis detection. Daily average tests in the state touched 50,000 in the past two weeks since the deployment of antigen tests. With 18,138 tests per million population, Maharashtra is now among the 24 states that have bettered the national average of 15,119 tests per million population in India.
It is estimated that over 3.3 lakh of the 23 lakh tests carried out in Maharashtra so far have been with the cheaper and easy-to-use antigen tests that give results within 30 minutes. The worry lies in the lower sensitivity of the test — ability to correctly identify those with the disease — that falls in the range of 50-80%. “As per literature, it can miss up to 50% of cases and therefore must be used in selected settings,” said Dr K Srinath Reddy, president, Public Health Foundation of India. A senior doctor said, “Antigen has to support RT-PCR. It cannot be the predominant mode of testing”.
As per state figures for August 3, Aurangabad — the district carrying out the highest per million tests in Maharashtra — performed 97% of its daily tests with antigen. Out of 11,990 tests, 11,638 were with antigen and barely 342 used RT-PCR. Overall in the state, Pune has been the biggest user of the antigen kits with over 93,000 tests done, followed by Aurangabad (50,000) and Mumbai (40,000). In Mumbai particularly, almost 50% of the tests are now performed with antigen.
Keeping aside concerns about sensitivity, a state official said that one should also consider the test’s specificity, or the ability to identify those without the disease, at 99%. “It’s helping us screen much bigger populations and use it in districts where RT-PCR is not readily available, say in Gadchiroli,” he said.
But Dr Subhash Salunkhe, a state technical panel member, said there are risks in testing too many asymptomatic cases with antigen kits: “We will miss patients, giving them a false sense of security. These tests shouldn’t be done for administrative satisfaction.” Dr Reddy said if a person has a high index of coming positive, he/she should be sent for RT-PCR directly. He also said that RT-PCR and antigen test numbers and positivity rates shouldn’t be mixed as that will dilute the real positivity numbers in the population.
Saurabh Vijay, secretary, medical education department, said there was no question of slowing RT-PCR. “Antigen gives us an indication, but we are pushing for maximum RT-PCR.”