Explained: Soon To Be Out Fast And Affordable Covid-19 Paper-Strip Test FELUDA; How Does It Work?

FELUDA, a COVID-19 test made by CSIR Institute of Genomics and Integrative Biology, Delhi, will soon be rolled out, Health Minister Harsh Vardhan said on Sunday (11 October).

The test has reportedly been approved by the Drug Controller General of India for a commercial launch.

The test has been named FELUDA after a fictional private detective from West Bengal created by renowned writer and filmmaker Satyajit Ray. It is an acronym for FNCAS9 Editor Linked Uniform Detection Assay.

Based on the tests on 2,000 patients, the test showed 96 per cent sensitivity (96 out of 100 positive samples show up as positive on the test) and 98 per cent specificity (98 out of 100 negative samples show up as negative).

“This compares favourably to the ICMR’s current acceptation criteria of RT-PCR kit of at least 95 per cent sensitivity and at least 99 per cent specificity,” Vardhan said, adding, however, that “an exact date on the availability cannot be specified yet”.

The FELUDA test is expected to cost between Rs 500 and Rs 600. Saliva or blood both can be used for testing, although saliva is preferred.

The FELUDA paper strip, after application of the sample, generates two lines for positive result and one line in case of a negative. It is similar to the pregnancy test, except that the pregnancy test detects protein while FELUDA detects nucleic acid.

The test uses indigenously developed CRISPR gene-editing technology. CRISPR, short form for Clustered Regularly Interspaced Short Palindromic Repeats, can detect specific sequences of DNA within a gene and uses an enzyme functioning as molecular scissors to snip it.

FELUDA is also reportedly the world’s first diagnostic test to deploy a specially adapted Cas9 protein to successfully detect the virus. Other CRISPR tests use CAS12 and CAS13 proteins to detect SARS-CoV2.

FELUDA uses the technology to identify and target the genetic material of SARS-CoV2, the virus that causes COVID-19. This is why it is able to differentiate SARS-CoV-2 from other coronaviruses even if genetic variations between them are minute.

The kit takes 45 minutes to give results. The RT-PCR test, on the other hand, takes 1.5 hours. The cartridge-based tests like TruNat give result in 60 minutes. A rapid antigen test kit, which interprets a positive or negative test in 30 minutes.

According to the CSIR, the FELUDA test matches accuracy levels of RT-PCR test which is considered the gold standard in the diagnosis of Covid-19, has a quicker turnaround time and requires less expensive equipment.