5,482 new cases, positivity rate below 9% for 3rd day in Delhi
On an average this month, the positivity rate recorded by rapid antigen tests was almost 17 percentage points lower compared to the more accurate RT-PCR test, according to data shared by health minister Satyendar Jain on Friday, as Delhi added fewer than 5,500 cases for the third straight day.
Over 23% of the samples tested using molecular tests like RT-PCR, CBNAAT and TrueNat returned positive this month, as compared to 5.8% of those tested using the rapid antigen test.
Although cheaper and faster, the rapid antigen test sensitivity can be as low as 50%, meaning it can throw up false negative reports for half of the patients who have the infection.
The highest positivity rate this month – which is an average of both molecular and rapid antigen tests – was recorded on November 15 when 15.33% of the samples returned positive. This was then a 140-day high. The positivity rate crossed 15.2% on November 8 as well, as per data shared by the Delhi government.
However, as per the data shared by the Delhi health minister, molecular tests recorded a positivity rate of 30% on November 7, reported in the health bulletin a day later.
A positivity rate this high was seen in Delhi only during the surge in cases in June-July before the introduction of the rapid antigen tests.
The highest positivity rate reported in the city was on June 13 when 36.9% samples had returned positive. Only 5,776 tests were conducted on the day in comparison to over 60,000 tests that are being conducted in the city at present.
“From a positivity rate of 30% on RT-PCR tests on November 7, it has now come down to about 15%, almost half. The positivity rate on rapid antigen test has also gone down by a third,” Delhi health minister Satyendar Jain said on Friday.
Meanwhile, the total positivity rate in Delhi remained below 9% for the third straight day on Friday, as 5,482 samples tested positive, of the 64,455 tests conducted on the day.
Delhi has consistently been adding fewer than the peak of above 7,000 fresh cases a day it saw during the second week of November.
As per the Delhi health bulletin on Friday, 98 deaths were added to the city’s overall fatality count, taking the overall toll in the city to 8,909.
“I do not think we can compare the positivity rates of the two tests as such, but the rapid antigen test is known to be only 50 to 60% sensitive even when the test is done properly. And if there is a 17% difference in the positivity rates of the two tests, it clearly shows we are missing out on diagnosing as many people through the less sensitive test. ,” said Dr Shobhaa Broor, former head of the department of microbiology at the All India Institute of Medical Sciences.