COVID RT-PCR test may be negative when diagnosed 7-8 days after high symptoms: Experts

If people showing clinical symptoms of COVID-19 are diagnosed seven to eight days after the initial onset of infection, there is a high possibility of a negative RT-PCR test, experts have said. While there are speculations that the false-negative rapid antigen test (RAT) results might be caused due to the new more virulent mutants’ ability to evade the testing, the director at the Institute of Genomics and Integrated Biology, New Delhi, Dr Anurag Agarwal,  clarified that these double mutants were “sequenced only from the samples that had positive PCR reports, and so, there is no possibility that variants cannot be detected through the PCR test.” In a statement to ANI, Dr Agarwal said, “Nothing can escape the double gene. People should know the PCR’s sensitivity is 70 per cent.”

The doctor at the Institute of Genomics and Integrated Biology explained that if people go for the test late, approximately seven to eight days after their symptoms are severe, there is a possibility of PCR (polymerase chain reaction) test coming negative but positive in CT (cycle threshold). “This is not about a new strain. It is the general behaviour of any virus,” Dr Agarwal said. He continued, “When people go for a test late, then many times PCR test comes negative in the nose and mouth. It is because the virus goes deeper inside the body.” Furthermore, he appealed to the people not to panic, saying that otherwise, the sensitivity of PCR never goes beyond 70 to 80 percent and the tests in most cases detected the COVID-19 virus, even when it mutates. “When you take all patients coming at all different stages there is nothing new. It is not because of the mutant strain of a virus,” he said. 

Speaking about the new variants of SARS-CoV-2,  namely B.1.617 and the newly detected ‘triple mutant variant’ B.1.618 with the E484K mutation, Professor Dr Saumitra Das of Indian Institute of Science, Bengaluru, said: ''The emergence of a new mutant is a long procedure. I do not think the emergence of new mutant can be correlated with changes in public behaviour like following the COVID guidelines or having strict quarantine rules.”

He stressed that people, however, had to be careful, although it cannot be said whether the ailment demanded a different treatment regimen or was more severe. “We should see how frequently these new mutations are coming out. These are two different issues that we should handle independently,” he said.

Director of the National Centre for Disease Dr Sujeet K Singh added, that it could be said from the hard-hitting surge that there was high mortality and severity detected in some places, but whether it is directly correlated with the mutants, “we are observing needs to be defined in a statistically valid manner.” He added, that it was perhaps the laxity in following the health safety measures that was behind the spike in COVID-19 cases.'' It is not the mutant alone that can contribute to the surge. Our laxity in COVID appropriate behaviour, our laxity in many other majors which are being planned have contributed to a significant level. The mutant could be a very, very small part of it,” stated Dr Singh.

Early outbreaks had 'no variants,' say experts

Speaking about the reports that the research on the double mutant was not conducted despite its early detection in October, Singh said, “such sequence was part of database pack in October. But in October with declining cases, there was no knowledge about this particular mutation being important. Nobody except an ‘antaryami’ person could have possibly thought this was important.” He added, that in December-January the outbreak first occurred in the states of Kerala and Maharashtra and the doctors had started looking for mutations in these areas. Kerala had the most severe outbreak at that time. This mutation was absolutely not seen in Kerala. So it was not related to the clinical outbreaks over there,” he said. “This mutation turned out to be important with papers coming out from California,” Dr. Singh continued, adding that North India, Punjab still does not have it. “Kerala does not have it. They also have outbreaks. So it is not a simple single-story,” he said.