February 25, 2021 9:50:37 pm
A YEAR’S worth of data on Covid-19 tests show that private laboratories have a higher positivity rate than government labs in Maharashtra. In private labs, out of 60.90 lakh samples tested, 18.76 per cent tested positive for the novel coronavirus. In government labs, on the other hand, 98.20 lakh samples were tested in government labs with 12.61 per cent positivity rate.
A high dependency on antigen tests by government labs may be responsible for lower positivity rate. Data from the public health department shows that out of 1.54 crore tests to date, 60.71 lakh were rapid antigen tests accounting for 40 per cent of the total testing pool.
Rapid antigen tests serve as a quick mass surveillance tool, producing results in a short duration, but have high chances of false negatives. This means they have a high rate of missing out on positive Covid-19 cases.
Based on the Centre’s advice, the state government last week directed all districts to reduce antigen tests and increase RT-PCR tests to account for 70 to 75 per cent. “We need to do away with dependency on antigen tests. We have been advising the government about this,” said Dr Sanjay Oak, chairperson of the Covid task force.
To date, real-time polymerase chain reaction (RT-PCR) — considered the gold standard for testing — has been used for 93.72 lakh samples, accounting for 60 per cent of total tests.
Across Maharashtra, 23.80 lakh test reports have come out positive for Covid-19, and another 1.35 crore were negative. Overall, the state’s positivity rate is 14.96 per cent; private labs have six per cent higher positivity rate than government labs.
In privately managed Suburban Diagnostics, chief scientist Dr Anupa Dixit said their use of rapid antigen test is limited to emergency hospital admissions where Covid-19 test is required before surgery, or when the BMC ropes in their lab for testing. “We do not use antigen for general public who come for Covid-19 testing, for them RT-PCR is used,” she said.
Dr Dixit added that positivity rate will also depend on the catchment area from where the sample was collected. Several districts said they still heavily relied on antigen testing for its convenience, even though they had the capacity for RT-PCR.
In Panvel corporation, daily tests range between 400 and 440, the corporation deploys antigen for 50 per cent tests. Dr Anand Gosavi, medical officer, said the state government had now asked them to use RT-PCR for at least 70 to 75 per cent tests. “We will be increasing RT-PCR tests soon,” he said. In Mira Bhayander corporation, out of 800 daily tests, half are undertaken using antigen kits.
In Dhule, civil surgeon Dr Manik Sangale said they were using antigen tests mostly in corporation areas and for routine screening in clusters. “In rural areas, we are using RT-PCR,” he said. The district tests 500 samples a day and plans to increase them to 1,000.
Until September last year, out of around 90,000 tests a day, RT-PCR contributed to two-third (50,000) and rapid antigen tests accounted for one-third. That gradually changed to 50:50 ratio this year in many corporations.
In Nandurbar, out of 500 daily tests, only 10 to 15 samples undergo antigen tests. Civil surgeon Dr Raghunath Bhoe said the district had the capacity to do 1,200 RT-PCR tests a day. “Until we exhaust that capacity, we don’t want to rely on antigen,” he said.
Dr Subhash Salunkhe, technical adviser to the state government, said with cases rising, mass testing should be undertaken, especially in pockets where there was a spike. “If antigen testing is used, districts need to strictly follow the norm of referring antigen negative samples for RT-PCR if the person is symptomatic.”
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