Explained: FELUDA paper strip test for coronavirus

Context: Union Health Minister rollout FELUDA paper strip test for coronavirus.

Tests on over 2000 patients during the trials at the CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB) and in private labs, showed that the test had 96% sensitivity and 98% specificity.

What is FELUDA?

• FELUDA is an acronym for FNCAS9 Editor-Limited Uniform Detection Assay.
• It uses CRISPR-Cas technology for the detection of genes specific to SARS-CoV-2 virus.
• In this method, a protein called FnCas9 and a guide RNA(gRNA) which helps in recognising the viral genes is used.
• If the patient sample has the viral gene, this gRNA-FnCas9 complex binds to the gene and using a paper strip this binding can be visualised.

How is the test done?

• The nasopharyngeal swab is collected
• RNA is extracted
• A single step RT-PCR is done
• The FELUDA mix is prepared by incubating the dead FnCas9 protein, guide RNA and the amplified viral DNA
• The dip stick is immersed in the FELUDA mix
• Gold nanoparticle on the strip bind to the FELUDA complex
• A protein called Streptavidin on the test line captures this gold nanoparticle bound-FELUDA complex
• Unbound gold particles are captured on the control line
• Colour develops on the test line and/or control line. One line indicates negative and two lines mean positive.
• The test takes about one to two minutes

Is it better than RT-PCR?

• RT- PCR equipment and reagents are costly and a technical expertise is needed.
• With FELUDA, the need for technical expertise is minimal and no requirement of expensive equipment, making it an easy to perform, point of care test.
• It saves space, time and money.

https://www.thehindu.com/sci-tech/science/explained-feluda-paper-strip-test-for-coronavirus/article32835460.ece?homepage=true