RT – PCR tests showing false negatives can be misleading

While RT-PCR tests on people showing significant symptoms of the Covid-19 disease returning negative even while CT scans confirm the infection are not new, the government-run Jayanagar General Hospital has had eight such cases in the past one week.

Two of these people have died and doctors say this is unusual given the low incidence. So many false-negatives in such a short span was not seen before, hospital authorities claim. “All eight cases had typical symptoms of Covid-19 and required hospital admission. We conducted a CT scan in all these cases which showed the infection. However, we lost two patients,” said Dr Sudha Heroor, nodal officer for Covid-19, Jayanagar General Hospital.

BBMP is currently randomly collecting swabs of positive patients for genomic sequencing, but sequencing needs to be done on these patients to check if they were infected by a different variant, the hospital said.

However, Dr CN Manjunath, nodal officer for lab and testing, state Covid-19 task force, said these could be among a cluster of such cases, and they may not be representative of all Covid positive cases.

“People who undergo RTPCR tests that throw up a false-negative result are treated as Covid-19 patients after CT scans show the infection. This is true of 5-8 % of cases across the state. Sometimes, repeat RT-PCR tests can be helpful. The syndromic approach based on CT scans and symptoms, irrespective of the RT-PCR report, is now well established,” Dr Manjunath said.

Doctors says false-negative reports can be misleading as patients tend to ignore symptoms given the heavy reliance on RT-PCR testing alone in Covid-19 management. RT-PCR is the gold standard to test for Covid-19.