RT-PCR tests to detect Covid not fully dependable

RT-PCR tests to detect Covid not fully dependable

Syed.Akbar@timesgroup.com

Hyderabad:11.06.2020

In a finding that could have widespread ramifications, researchers at Centre for Cellular and Molecular Biology (CCMB), Hyderabad, have found that about 50% of Covid-19 positive samples tested through the standard RT-qPCR test may not yield the correct result.

Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) test has been recommended by the WHO and Centers for Disease Control and Prevention (CDC) and is used globally to detect the virus.

The CCMB scientists found a high percentage of false negative cases while comparing the RT-qPCR with a new test method developed by the them. The new test - R-T-nPCR - is not only cost-effective but can be conducted on a large number of people in a short time, the researchers said. is “We found that taking both standard RT-qPCR tests together, the RT-nPCR test was able to correctly identify 90% of samples detected as positive by RTqPCR. It also detected 13% samples as positive among samples that were negative by the standard RT-qPCR test (likely false negatives),” the scientists said in their research paper which has been uploaded on an online pre-print repository for biological sciences ‘bioRxiv’.

“Based on the experimentally measured false negative rate by RT-nPCR tests from this study, we estimated that as many as 50% of the positive samples may escape detection in single pass testing by RTqPCR in an actual testing scenario,” they added.

The new method uses RTnested PCR and is equally sensitive as RT-qPCR. This method needs a simple PCR machine. It increases the possibility of many more labs doing Covid-19 tests, thereby expanding testing capacity. RT-qPCR requires an expensive qPCR machine, which is not found in many labs in the country.

“The CCMB method is suitable for largescale surveillance,” the researchers claimed.