MUMBAI: The daily positivity rate for Covid-19 in the city appears to have seen a decline in the last few days. According to a state government official, “A decline in positive cases despite an increase in testing could be a good sign, but one shouldn’t be eager to celebrate this. These numbers have to be steady and Mumbai is still not testing a lot.”
Besides, a senior doctor said that the deployment of rapid antigen testing, which is known to have a higher false negativity rate, could be pulling down the overall positivity numbers. “More antigen tests mean more people being tested. That expands the denominator and brings down the overall positivity rate, but we must remember that up to 50% of the samples can throw a false negative result in antigen tests,” the senior doctor said. Any symptomatic person coming negative in an antigen test is followed up with a RT-PCR test, considered the gold standard.
Civic officials, however, said that unlike Delhi, the lion’s share of tests in Mumbai were still being done with RTPCR. “Out of an average of 6,000-6,500 tests done every day, merely 700-800 are done using antigen,” said an official.
The massive uptake of the cheaper and quicker antigen tests across the country has in fact now given rise to concerns about the possibility of larger community transmission in instances where those testing negative are not followed by with a confirmatory diagnosis with RT-PCR. In Delhi, over 18% of negative rapid antigen results have come positive under RT-PCR.
Data for the state doesn’t give a clear trend though, where positivity rate seems to be between 22-25% on most days in July. The state has been conducting an average of 35,000 tests since the last few days. However, officials said even if testing numbers have gone up, that is largely focused on urban centres whereas cases are spreading to rural parts, as seen in Solapur and Pune.
Meanwhile, leader of opposition and former chief minister Devendra Fadnavis on Tuesday also released comparative data between tests conducted in Delhi, Mumbai and Maharashtra to state that Delhi has brought down its positivity rate from 35% to 6% after testing was scaled up.
Fadnavis said that Delhi was conducting over 20,000 tests a day compared to the average of 5,500 done by Mumbai in the last 19 days of July. “Number of tests in Maharashtra and Mumbai remain stagnant. After aggressive testing, 30-35% infection rate went down to 6% and number of deaths too reduced in Delhi,” he said.
Besides, a senior doctor said that the deployment of rapid antigen testing, which is known to have a higher false negativity rate, could be pulling down the overall positivity numbers. “More antigen tests mean more people being tested. That expands the denominator and brings down the overall positivity rate, but we must remember that up to 50% of the samples can throw a false negative result in antigen tests,” the senior doctor said. Any symptomatic person coming negative in an antigen test is followed up with a RT-PCR test, considered the gold standard.
Civic officials, however, said that unlike Delhi, the lion’s share of tests in Mumbai were still being done with RTPCR. “Out of an average of 6,000-6,500 tests done every day, merely 700-800 are done using antigen,” said an official.
The massive uptake of the cheaper and quicker antigen tests across the country has in fact now given rise to concerns about the possibility of larger community transmission in instances where those testing negative are not followed by with a confirmatory diagnosis with RT-PCR. In Delhi, over 18% of negative rapid antigen results have come positive under RT-PCR.
Data for the state doesn’t give a clear trend though, where positivity rate seems to be between 22-25% on most days in July. The state has been conducting an average of 35,000 tests since the last few days. However, officials said even if testing numbers have gone up, that is largely focused on urban centres whereas cases are spreading to rural parts, as seen in Solapur and Pune.
Meanwhile, leader of opposition and former chief minister Devendra Fadnavis on Tuesday also released comparative data between tests conducted in Delhi, Mumbai and Maharashtra to state that Delhi has brought down its positivity rate from 35% to 6% after testing was scaled up.
Fadnavis said that Delhi was conducting over 20,000 tests a day compared to the average of 5,500 done by Mumbai in the last 19 days of July. “Number of tests in Maharashtra and Mumbai remain stagnant. After aggressive testing, 30-35% infection rate went down to 6% and number of deaths too reduced in Delhi,” he said.
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