For reliable antibody testing kits , India will have to make its own, according to independent epidemiologists and biotechnologists.
A day after the Rajasthan government said that it would stop antibody tests because they were returning inaccurate results, the Indian Council of Medical Research announced that it had advised putting such tests on hold because it was generating widely varying results. The ICMR on Wednesday said it had forwarded a “protocol” for rapid antibody tests to all States, but did not specify the details.
Much like home-based pregnancy tests, antibody tests are valuable because they give results quickly and only needs a pinprick’s worth of blood. However, they can only detect antibodies produced by the immune system in response to the virus and this can take as many as 7-14 days to manifest. “The initial expectation was that an antibody test would soon be available. But it was the PCR technology that came first. That’s also due to the fast moving nature of the virus,” said Iype Joseph, epidemiologist with the Rajiv Gandhi Centre for Biotechnology.
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The PCR technology is confirmatory because it identifies the SARS COV-2 based on genes, whereas the presence of viruses have usually been detected via antibody kits by the proteins produced by the virus’s genes.
An antibody test only tells you whether a person has ever been infected by the virus. These antibodies that are produced are not necessarily specific to SARS COV-2 and could even be generated by a variety of other pathogens. “There are other 4 other common coronaviruses and antibodies could be generated to that too. So far, nobody has found a protein that’s specific to SARS COV-2.”
Reliability in doubt
The ICMR’s current recommendation is to test those who show symptoms such cough, fever and breathlessness and even a sore throat. After quarantining for 14 days, an antibody test is to be done and if positive, the person ought to be tested by RT-PCR.
The ICMR has underlined that tests are a surveillance tool. The utility of the test was evolving and its value was dependent on field conditions. They were not a replacement for RT-PCR tests.
However, with the accuracy widely ranging from 5% to 71%, there are questions on whether they can reliably help indicate the spread of the infection.
All kits need to be validated by the National Institute of Virology, Pune. They test two things: Are the kits detecting antibodies at specified intervals after an infection, mirroring when antibodies actually show up in people with confirmed coronavirus ( COVID-19 ) infections? And do they falsely respond to the presence of other pathogens? It is not clear how tests validated by the NIV began showing widely discordant results for them to be paused by the ICMR. “We need tests that are locally developed and validated,” said Dr. Joseph.
“The need of the hour is to have rapidly deployable RT PCR kits. If we can reduce the time taken for analysis, or have a paper-based strip that can detect the virus, it would be more useful,” said Asha Kishore, Director, Sree Chitra Tirunal Institute for Medical Sciences and Technology. Her organisation has developed a rapid PCR test that awaits final approval from the ICMR.
Renu Swarup, Secretary, Department of Biotechnology, said that India’s challenges with diagnostic kits were temporary.
“There are at least seven Indian manufacturers of these kits awaiting approval from the National Institute of Virology and we are hoping to be able to produce at least a million kits by end May.”