Traditionally used in HIV testing, the enzyme-linked immunosorbent assay (ELISA) technique will find use in Covid-19 testing if the Centre okays its use in India. Suresh Vazirani, founder chairman of Transasia Bio-Medicals, an Indian MNC, told Businessline that the company has applied for an import licence from the Drug Controller General of India (DCGI) on May 4 to make ELISA kits available in India — under the brand name ErbaLisa — through its US subsidiary Calbiotech.

Vazirani also said that on May 4, three kits (each kit can process 96 samples at a time) have been sent to the National AIDS Research Institute in Pune for local validation. “Our ELISA kits, which took close to one-and-a-half months for development, have received USFDA and CE approvals two weeks back. They demonstrate sensitivity and specificity of over 98 per cent. Now, we expect Indian validation results to be in by 8 to 10 days, which will enable us to locally manufacture kits in our facilities at Daman, Andhra Medtech Zone and Sikkim. Currently, we have the capacity to manufacture up to 30,000 kits in a month and can look at scaling up,” he said.

Similar to rapid antibody tests, ELISA uses antibodies in the blood to detect if a person has been infected with Covid-19, but is way more accurate since the test is conducted in a lab-setting. “We are intending to price it at ₹ 500 per test, which is lesser than the ₹ 600-800 that was spent on buying the rapid kits from China, which were eventually deemed faulty by the government. ELISA is a superior technology, whereas finger-prick rapid antibody test kits that are imported or domestically produced are bound to display less accuracy, as their test design is crude,” he said.

ELISA will help in testing individuals who show no symptoms of Covid-19 but are or have been infected by the virus to determine if they have developed any kind of immunity. “We test them for IgG antibodies for Covid-19 as they peak in person between 10 and 14 days post infection and last for more than six months in a person’s body, probably for even life, after they have been infected with the virus. This will help in mass surveillance of asymptomatic persons too,” he added.

Most hospitals, labs and blood banks, Vazirani pointed out, have ELISA machines for their routine HIV and viral Hepatitis testing, and Covid-19 kits can be used in the ELISA set-ups as well. One ELISA set-up used to run these tests can cost close to ₹3 lakh.

Can’t be done at home

Vazirani explained how the test works: “Each kit consists of 96 wells coated with Covid-19 specific antigen, which is derived from the virus and grown artificially in culture. Blood serum from a suspect sample is inserted in the well and the machine simultaneously processes up to 96 samples to give their antibody positive or negative reading based on result of threshold of colour-based absorbency generated after adding a reagent to the sample. If absorbence is over the threshold of 0.9, then the sample is antibody-positive, while anything below is negative.”

In documentation filed with the Indian drug regulator, the company has clarified that ELISA testing serves only as an aid to diagnosis and its results should be interpreted in tandem with a patient’s history, physical findings and other diagnostic procedures. The test cannot be conducted at home, the company has warned.

The company has supplied 5,000 kits to Italy for testing close to five lakh people. It is also supplying to Germany and UK to conduct 500 tests each for evaluation. Brazil, too, has ordered up to 2,000 kits to test two lakh persons. The company is also eyeing a massive order from a private lab chain in the US, Vazirani said.

ELISA kits also have a role to play in plasma therapy, Vazirani said. “The plasma donors have to be checked for antibodies and those with more antibodies will be the preferred candidates for donating plasma,” he said.

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