Rajasthan health minister Raghu Sharma told reporters today that the rapid test kits had only 5.4 per cent accuracy. Besides Rajasthan, Kerala and Tamil Nadu have also expressed their unhappiness with the results, sources said.

Rajasthan conducted around 170 tests in the COVID-19 hotspots, starting with Jaipur, since Friday. The kits were used for testing of patients who have already tested positive for coronavirus. But the rapid test kits found them negative, which raised questions about the credibility of these kits, the minister said.

The Indian Council Of Medical Research, the country's nodal body in the fight against coronavirus, has asked all states not to use the new rapid antibody test for COVID-19 for two days. The ICMR said it would investigate the issue of faulty rapid testing kits and would "definitely not ignore this defect".

Beijing last week denied that the kits were not up to mark, saying they attach "great importance to the export of medical products". The stricter regulatory measures introduced involve registration certificate for medical device from the State Food and Drug Administration and meeting quality standards of the importing countries.

Earlier this month, the government had procured around 7 lakh Rapid Testing kits from China and distributed across the country after the ICMR advised testing for all people in the COVID-19 hotspots. The testing started four days ago.

Many states still do not have adequate testing facilities for the current BT-PCR tests, which rely on swabs from the patients. The tests have to be processed in a laboratory and takes up to six hours. In a rapid test kit, the results are available within 30 minutes at the most.

Sources said the ICMR had agreed to the use of Rapid Testing Kits after repeated requests from states. Besides being time consuming, the RT-PCR tests are also not cost effective and therefore were not suitable for random tests.

In a letter to states on April 17, the ICMR had made it clear that antibody tests can only be a supplementary tool. Antibody tests cannot replace the RT-PCR test for COVID-19 diagnosis, the top medical body had said. "We have been advising states that antibody tests are not recommended for COVID-19 diagnosis. Data on antibody tests still emerging and its utility is still evolving, sources in the ICMR said.

The Rapid Test kits, which cost around Rs 600 each, are basically blood tests that look for antibodies to the coronavirus, which is the final evidence that a person is infected and works even for people who are asymptomatic.