Coronavirus: Why India dumped rapid testing for mass Elisa-based tests

KEY HIGHLIGHTS

• ICMR-NIV's Elisa Test kit gets government nod; to be produced by Zydus Cadila

• Biocon's Syngene and Transasia to also start production, awaits regulatory approvals

• 12 US companies already got Emergency Use Authorisation (EUA) to make such kits

• This blood test quickly determines level of antigens in human body

• Can help in mass testing to know development of herd immunity

With India giving green signal for commercial manufacture of Elisa-based antibody detection test for coronavirus, more Indian companies are likely to enter the market soon. Elisa stands for Enzyme-linked immunosorbent assay. The players likely to make foray in such tests segment are Biocon's Syngene and medical devices maker Transasia.

Health Minister Dr Harsh Vardhan said on Sunday that technology for an indigenous Elisa test named "Covid Kavach Elisa" developed by the Indian Council of Medical Research (ICMR)-National Institute of Virology (NIV) at Pune has been transferred to Ahmedabad-based drug maker Zydus Cadila for mass scale production. It was validated at two sites in Mumbai and can test 90 samples together in a single run of 2.5 hours. Zydus Cadila is yet to divulge details of its production plans. Last week, Biocon's chairman Kiran Mazumdar Shaw told Business Today that Biocon's contract research company Syngene International has developed a fully indigenous prototype and will soon get it evaluated by ICMR and other regulatory agencies in India.

Mumbai-based medical devices company Transasia Biomedical's German subsidiary Erba Mannheim has already got clearance from the US and Europe to make COVID-19 antibody ELISA kits. Reportedly, Transasia has plans to make the kits in its manufacturing plants in Daman and Sikkim and at a planned Covid-19 new facility in Andhra Pradesh, once it gets Indian regulatory approvals. Erba Mannheim claims each kit, developed in one and half months, can test 100 samples an hour, with an accuracy rate of 98%.

How does Elisa-based antigen test work?

Elisa test platforms have been used for many decades to detect infectious diseases like Hepatitis-B, Hepatitis-C and HIV, though so far there are no approved Elisa tests for coronavirus.

Serology tests can detect the body's immune response to any infection caused by the virus rather than detecting the virus itself. In the early days of an infection, when the body's immune response is still building, antibodies may not be detected. Viral antigens stimulate human body to produce antibodies. Elisa tests can detect these antigens by measuring blood components like IgM and IgG. The test will determine whether the blood sample has developed antigens (in IgM) during onset of disease and long term immunity after a few days of infection with the IgG tests. While real time RT-PCR is the frontline test for clinical diagnosis of SARS-CoV-2, antibody tests are critical for surveillance to understand the proportion of population exposed to infection. It will help find if 'herd immunity' is developing in a population.

Mass Testing

"The advantage is it is easy to test large population in non-laboratory set ups, will be cheaper than RT-PCR tests, and can determine the exact status of disease in an infected person," according to Kiran Mazumdar Shaw.

Elisa-based testing is easily possible even at district level as the kit has inactivated virus and does not require labs to take samples. There are also minimal bio-safety and bio-security requirements as compared to the real-time RT-PCR test evaluations. The test has an advantage of having much higher sensitivity and specificity as compared to the several rapid test kits which have recently flooded the Indian market. The test will help healthcare professionals identify whether individuals have developed an immune response to SARS-CoV-2 virus. The presence of antibodies conveys a level of immunity that would prevent or minimise the severity of re-infection as well as the duration for which immunity lasts.

US already producing

In the US, the regulatory agency Food and Drug Administration (USFDA) gave Emergency Use Authorisation (EUA) two weeks ago to about a dozen companies for producing such serology tests. The firms are Abbott, Roche, Autobio, Bio-Rad Laboratories, Cellex, Chembio Diagnostic Systems, DiaSorin, EUROIMMUN, Mount Sinai Hospital Clinical Laboratory, Ortho-Clinical Diagnostics and Wadsworth New York. Similarly, regulatory agencies in Europe have allowed many companies to experiment such tests. Products of many of these companies have shown above 90 percent accuracy - in sensitivity and specificity measurements.

At present, RT-PCR (reverse transcription-polymerase chain reaction) and CB-NAAT (Cartridge-based Nucleic Acid Amplification used to test for tuberculosis) are the two tests being used to detect coronavirus. But their turnaround time is long, making large scale testing difficult. So far, India has been able to test only 16.73 lakh samples from its 130 crore plus population. India had imported large volumes of Rapid Test kits, but most turned out to be faulty and the government had to junk them.

Also read: Coronavirus vaccine: List of 5 COVID-19 treatment frontrunners

Also read: 345 govt institutes, 131 private hospitals conduct coronavirus tests: ICMR