KOLKATA: With just a little over a month to go for two years of the pandemic in Bengal, there have been 2.3 crore Covid tests performed in the state since end February 2020, according to data released by the health department.
Over a crore of these were rapid antigen tests (RAT), of which 10.3 lakh - or about 10% - were performed in the last month alone, during the Omicron-fuelled third wave.
Over 50% of all Covid tests performed in Bengal in the past month were antigen tests. Were home tests factored in, the figure would have been much higher, experts believe. "With a huge number being affected this time, rapid tests helped detect the positives faster," said intensivist Sauren Panja. "Unfortunately, few of those who got tested at home uploaded the results, which has kept the real number hidden," he added.
Over 21 lakh tests were conducted in Bengal since December 28 last year, when Covid cases started rising, with over 10 lakh of those being antigen tests. And 5.8 lakh of those 10 lakh RAT tests were done in the last fortnight alone, reveals the data.
RAT gained favour during third wave
According to ICMR, commonly used lateral flow tests, such as rapid-antigen tests (RAT) and home-antigen tests (HAT), help in early detection of Covid-19, between the third and the eighth day (when the viral load is maximum). During the third wave, it emerged as the backbone of testing. However, RT-PCR tests - which were considered the gold standard test during the previous surges - can detect certain non-infective RNA particles even after the eighth day, leading to positive results.
The data shows that during the first two waves of the pandemic, the thrust was mainly on RT-PCR. But this gradually shifted in favour of RAT during the third wave, something acknowledged by chief minister Mamata Banerjee as she was announcing Covid relaxations on January 31.
Till January 17, the proportion of RT-PCR tests was significantly higher than RAT tests. But over the next few days, Rapid antigen tests were more than 50% of the total daily tests performed.
Banerjee had said that the faster transmissibility of Omicron made RAT tests - which throw up results in minutes - an effective tool.
