West Bengal: RT-PCR recheck to find false Covid-19 negative – Times of India

Kolkata News
KOLKATA: The state is all set to identify those who had tested negative for Covid in rapid antigen tests and make them go through RT-PCR tests to trace false negatives. This follows ICMR’s revised guideline on Covid testing. On Saturday, the health department asked all district magistrates and chief medical officers health (CMOH) to intensify the search for missed positive cases through follow-up RT-PCR tests for all rapid antigen test negative cases. The test should be done on those who had taken the rapid antigen test five-10 days ago.
Sources at the department said that only those people who were symptomatic but their rapid antigen test report was found negative were being re-checked by RT-PCR.

“Following the revised ICMR guideline, all district health officials and administrations have been told get all rapid antigen test negative cases re-tested through RT-PCR,” said a health department official.
“While RT-PCR is more sensitive, rapid antigen test is known for false negative reports, especially in people who do not have symptoms. Therefore, missing positive cases is higher in rapid antigen test than RT-PCR. It is a good move to get negative reports ratified by RT-PCR,” said microbiologist Pratip Kumar Kundu, former director at School of Tropical Medicine, Kolkata.
The state started conducting rapid antigen tests on July 28 with only 1,183 tests. The number started rising in August when out of the 9,13,460 tests that month, 4,01,402 were through rapid antigen testing. Till Saturday, out of the total 63,82,278 tests, 28,52,391 had been done by rapid antigen tests.
“Initially, the rapid antigen test kits were of good quality. But of late ,many companies have forayed into rapid antigen test kit manufacturing and we have come across low-quality kits with less than 60% sensitivity. This might give rise to false negative cases,” said Pradip Mitra, former director of medical education who is now officiating as the coordinator of Covid management and containment committee.
While in Kolkata rapid antigen tests are being carried out through KMC, in districts they are in operation in different government health centres. Medical colleges in Kolkata are using it only in specific cases, like before an emergency surgery.
“In rapid antigen tests, the sensitivity is poor — around 50% to 70%. Hence, negative results in rapid antigen tests have the chance of actually being positive in 30% to 50% of cases. So it is always good to re-test negative results of rapid antigen tests with RT-PCR,” said Prabhas Prasun, associate professor at Institute of Child Health.
According to Institute of Post-Graduate Medical Education & Research (IPGMER) professor Diptendra Sarkar, this is a good move and will help to identify more Covid cases. “Rapid antigen tests were never strongly recommended other than for screening of people in a cluster or where an immediate result was necessary. They have a lower sensitivity than RT-PCR and obviously lead to more false negative reports,” said Sarkar.
It won’t be particularly difficult to identify and trace those who have taken rapid tests, felt experts. But only those who have taken the rapid test within the last five-10 days ought to be made to take an RT-PCR now since the virus can no longer be traced in those who took the test earlier.
“The virus can be traced within the first five to 10 days of symptoms. The Covid viral load is at its peak on the seventh day. While a rapid test has a 50% sensitivity rate, in case of RT-PCR, it’s 70%,” Sarkar said.

Source: https://timesofindia.indiatimes.com/city/kolkata/rt-pcr-recheck-to-find-false-cov-ves/articleshow/79699397.cms