india

Updated: Apr 27, 2020 21:15 IST

The Indian Council of Medical Research (ICMR) asked states on Monday to stop using rapid tests kits made by two Chinese companies and return them.

In a letter to chief secretaries, ICMR additional director general GS Toteja said the scientific body has evaluated the performance of the kits, which were initially seen as crucial in efforts to speed up Covid-19 testing, and found wide variation in results.

ICMR has tested the kits of Guangzhou Wondfo Biotech and Zhuhai Livzon diagnostics in field conditions, the letter said.

“The results have shown wide variation in their sensitivity despite early promise of good performance for surveillance purposes,” it said.

He said states should stop using kits procured from these companies and return them so that they could be sent back to the suppliers.

Toteja said several states procured rapid antibody test kits even as ICMR made them available at the clear instruction that these kits were to be used only for surveillance purposes.

On April 16, ICMR received a consignment of 550,000 of these test kits from the two Chinese companies.

On April 21, ICMR put on hold the use of rapid testing kits after complaints from several states. The first came from West Bengal, which said the kits returned ‘inconclusive results’.

Soon, Rajasthan, which was the first to start using the kits on April 18, found that patients already confirmed through reverse transcription polymerase chain reaction (RT-PCR) tests were reported as negative by the rapid test kits.

After India halted its use, both the Chinese companies that exported the kits issued a statement saying their testing kits were of optimum quality and they would cooperate with the Indian authorities to get to the cause behind the inaccurate test results.

The principle mechanism of how the blood tests work is one of the reasons they are turning out to be complicated: these detect antibodies that an infected person’s body creates in response to the virus, instead of detecting the virus itself – which is the case in the swab tests.

Antibodies can take days to show up in the blood, scientists say. In a yet-to-be peer reviewed paper comparing 12 such blood test kits, American researchers found that the accuracy of positive results ranged between 81.8-100% after 20 days of a person first showing symptoms.

The accuracy of negative results in those not infected was in the 84.3-100.0% range.