The ICMR had to halt surveillance testing of COVID-19 at a critical juncture in India as the rapid test kits procured from China were reported to be faulty. Rajasthan complained that they only showed 5 per cent accuracy and other states also reported variation in test results.
Now, two Chinese companies — Livzon Diagnostic Inc and Wondfo — which supplied 5.5 lakh kits to India on April 16, say that they were validated by NIV, Pune and then cleared by ICMR for supply. They say they are investigating reports of malfunction and Livzon says it is willing to coordinate "with related Indian government departments for investigation."
News 18 is in possession of the responses of the two companies. Both companies provide a similar defence that kits have to be used at a certain temperature. Livzon says its test kits are to be stored between 2 to 30 degrees and should not be frozen. Wondfo says the test cassette should be used within one hour of taking out of the foil and the testing agent should be resealed each time.
But what is most significant, is that both companies quite clearly say that these rapid test kits may not detect antibodies at all even in an infected person due to a "window period" between which a person is infected and antibodies are created. So, they say a negative test should be followed up by a nucleic acid test (RTPCR test) for surety. A negative test, they say, doesn't negate an infection.
Livzon goes a step further and adds that rapid antibody test is not recommended for screening general population. "Results should not be used as a sole basis of diagnosis of infection of novel coronavirus."
But India is not using rapid test kits for diagnostic purposes. It's is using rapid test kits for surveillance to check how much of population has developed antibodies to get a sense of how widespread the infection is even if asymptomatic. However, if rapid antibody tests are prone to so much variation, question arises about their usage in the first place.