The Feluda test, a coronavirus detection test developed by the Council of Scientific and Industrial Research (CSIR) and to be commercialised by Tata Sons, will be commercially available in laboratories this month.
“It should be available anytime soon this month. All the formalities are completed,” Shekhar Mande, Director General, CSIR, told The Hindu .
The test, which still requires a nasal swab to be collected and sent to a lab, promises to be quicker than the gold-standard test because it doesn’t need the expensive RT-PCR (Reverse transcription-quantitative polymerase chain reaction) machine that can set back a lab by at least ₹25 lakh.
A smaller, cheaper more portable machine called a thermocycler, which costs around ₹25,000, is employed and once the viral RNA is extracted, it takes anywhere from 45 minutes to an hour to confirm presence of the virus.
FELUDA, that stands for FNCAS9 Editor-Limited Uniform Detection Assay, is also unlike antigen tests in that it uses a CRISPR-cas9 based system and therefore more accurate in detecting the virus.
CRISPR-cas9 is a genome-editing tool whose discovery won the Nobel Prize for chemistry this year. Though initially conceived to treat sickle-cell disease, in the FELUDA the cas9 enzyme, it can be used to hone in on a specific sequence of DNA (in this case unique to the coronavirus) and thereby infer its presence.
Compared to the RT-PCR test, it’s reportedly cheaper — about ₹500 per test compared to ₹1,200-₹1,600 for RT-PCR, according to current estimates though that would be known only once it’s commercially available in laboratories later this month.
A major factor that determines how quickly labs are able to process tests is in how quickly they are able to extract viral RNA. There are varying approaches and good labs with trained personnel can do the job within 15 minutes but can be a complex process in places with limited facilities.
While a paper-based test might resemble the home-based pregnancy test that doesn’t need an intervening lab, the FELUDA, isn’t yet at that stage and the paper is only one part of a series of steps to confirm the virus presence. The paper strip when dipped into a specially created chemical soup returns two blue lines if the virus is present and a single one if negative. “This bit on the paper takes two minutes but the several other steps can take time. However, the simpler machines and the standardised processes after the RNA is extracted make the FELUDA approach more scalable in a wide range of settings,” said Dr. Anurag Agrawal, Director, CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), whose scientists have developed the test.
In theory a saliva sample can be used in a FELUDA-style system but current government regulations don’t permit the use of such tests because there isn’t a standardised process to extract RNA and — the wisdom goes — can lead to many more false negatives. “Our future plans do involve being able to make it a purely home-based test but that’s still some time away,” Mr. Mande said.