Haryana relies on RT-PCR technique, conducts 65K tests

Sushil Manav

Tribune News Service

Chandigarh, May 13

With Haryana differing from the Centre over its tweaked guidelines on discharge of mild, very mild and pre-symptomatic Covid cases without testing 10 days after the onset of symptoms if they are not running fever for the past three days, the focus has now shifted to various tests being conducted to diagnose the virus.

Haryana has so far conducted 65,785 tests using real-time reverse transcription-polymerase chain reaction or RT-PCR technique ever since the Covid outbreak. Of 65,785, 59,890 samples tested negative and result of 5,102 is awaited. As many as 793, including 14 Italian nationals, tested positive.

Pool sampling

In pool testing, samples from two to five people are collected and tested in a single unit. If the pool tests negative then all individuals are regarded as negative. But if the pool sample is positive each person in the pool is tested individually to find out who is affected. This helps increase the testing capacity and saves time, money and manpower.

Single step, 2-step technique

Dr Chaudhary explains that the one-step technique involves subjecting the extracted RNA of the sample to reverse transcription and then PCR amplification in a single test tube while in the two-step technique, the reverse transcription and PCR are done separately. “The first one is a preliminary test, while the second is confirmatory. If the first comes negative, there is no need for the second,” Chaudhary adds.

CB-NAAT machines

Cartridge Based Nucleic Acid Amplification Test (CB-NAAT) machine is fully automatic machine and this also uses PCR technique, though not after reverse transcription.

“A different cartridge is used for testing Covid by using CB-NAAT machines. Also called GeneXperts, CB-NAAT helps getting results in less than an hour, while the RT-PCR takes six to eight hours,” says Chaudhary.