A new coronavirus diagnostic method, using a low-cost portable unit developed by researchers at the Indian Institute of Technology (IIT), Kharagpur, has been approved by the Indian Council of Medical Research (ICMR) after testing with patient samples showed an accuracy level slightly lower than the gold standard RT-PCR method at a fraction of the cost.
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The machine cost less than ₹5,000 to make and the test kits would each cost about ₹500, IIT-Kharagpur researchers told journalists on Wednesday. Once the viral RNA was extracted, the testing process took about one hour. The IIT was in discussion with commercial manufacturers and start-ups, and hoped that the government would also subsidise the cost of test kits, they said.
In parallel testing with 200 samples containing a wide range of viral loads, IIT-Kharagpur’s COVIRAP method correctly detected 108 out of the 115 positive samples identified by an RT-PCR machine, and 83 out of 85 negative samples, meaning that it has a 94% sensitivity and 98% specificity in comparison to RT-PCR.
“Initially, we were very sceptical, but we were delighted when it worked. The assays are comparable [to RT-PCR],” ICMR virologist Mamta Chawla Sarkar told journalists on Wednesday.
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“This assay holds the capability of detecting extremely low levels of viral loads that any other method based on similar principles of testing... In practice, this means that very early stages of infection can be detected, thereby isolating the patient and arresting the uncontrolled spread of infection in the community via asymptomatic patients,” she noted.
Only ₹5,000 to make it
Unlike the RT-PCR machine, which could cost up to ₹25 lakh, and needed to be operated by a molecular biologist, the COVIRAP machine cost the IIT researchers only ₹5,000 to make and could be manufactured at even lower cost if economies of scale were applied by commercial manufacturers, said lead researcher and IIT professor Suman Chakraborty.
‘Ideal for use in rural areas’
“The COVIRAP method requires very little equipment, and is ideal for use in rural areas with limited facilities. The portable unit can even be placed on a table in a field, without the need for an air-conditioned laboratory. It can be operated by rural youth with minimal training,” said Dr. Chakraborty. However, the viral RNA would still have to be extracted in a lab.
The machine employed an isothermal nucleic acid amplification method, which did away with need for a thermocycler, he said. Once the sample was processed in the machine after being mixed with solutions developed by the IIT team, treated paper strips -- similar to the pregnancy strips -- are dipped into it, and the emergence of coloured lines will depict the presence of the virus. A mobile app has been developed to analyse the strips placed in a hand-held unit, in order to minimise human error.
Isothermal nucleic acid amplification employs an approach similar to one in RT-PCR and has its advantages and disadvantages. Other laboratories, including those of the CSIR (Council of Scientific and Industrial Research) and the Department of Science and Technology have designed devices based on this approach but none yet have been cleared by the ICMR and reached the stage of commercial manufacturing.
FELUDA test
FELUDA, a kit developed by the CSIR-IGIB (Institute of Genomics and Integrative Biology), also is a ‘paper strip based test’ but employs a gene editing technology called CRISPR-cas9. Like COVIRAP, it too claims to deliver results in an hour--as compared to 3-4 hours in an RT-PCR-- but are ultimately laboratory based tests and depend on skilled personnel to extract the nucleic acid RNA from a nasopharyengal sample prior to the actual testing. FELUDA, cleared by the Drug Controller General of India and the ICMR, has been licensed to Tata Sons and is expected to be commercially available later this month.
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The COVIRAP method could be used to diagnose diseases such as influenza, malaria, dengue and tuberculosis, Dr. Chakraborty said.
