India's Feluda test put CRISPR on a paper strip for $6.75 Covid diagnosis

In October 2020, scientists at Delhi's CSIR-Institute of Genomics and Integrative Biology (IGIB) unveiled Feluda, a paper-based Covid-19 test named after an Indian fictional detective. It used CRISPR gene-editing to detect the virus and was to be manufactured by Tata — potentially the world's first paper-based Covid-19 test on the market. The kit returned results in under an hour at about 500 rupees ($6.75), against PCR tests costing up to 2,400 rupees.

Tried on samples from about 2,000 patients, including known positives, it showed 96% sensitivity and 98% specificity — the accuracy profile of the gold-standard PCR — and India's drug regulator cleared it for commercial use. Principal scientific adviser K. Vijay Raghavan called it 'a simple, precise, reliable, scalable and frugal test'; IGIB director Anurag Agarwal said it had 'the reliability of the PCR test, is quicker and can be done in smaller laboratories which don't have sophisticated machines.'

The trick was precision: gene-editing works like a word-processor cursor that can remove or add a single genome letter, so as a diagnostic the CRISPR complex latches onto the gene letters carrying the coronavirus signature, highlights them, and produces a paper read-out. Researchers and global-health experts expected it to displace rapid antigen tests, which were cheaper than PCR but generated more false negatives; a Harvard research fellow called it 'an important step' toward making testing widely available.

PCR needed accredited laboratories and cost up to 2,400 rupees, while cheap antigen tests missed cases — India needed PCR-class accuracy at scale.

CRISPR's single-letter precision turned the detection step into a paper read-out, removing the need for sophisticated machines.

Manufacturing through Tata gave a government-lab invention a path to national scale.

Frugality is a design target, not a compromise: strip PCR-grade accuracy down to paper and you can test where the machines aren't.

India's drug regulator cleared the Feluda test for commercial use, with Tata set to manufacture it; researchers expected it to replace less accurate antigen tests in smaller laboratories.