As part of his daily press briefings, Kerala chief minister Pinarayi Vijayan on March 28 evening announced that the state would start conducting rapid antibody tests on suspected Covid-19 patients.

The next morning, he reiterated this on Twitter. “Blood samples of those under observation will be collected to detect possible community transmission,” he said.

So far, India has used the RT-PCR or reverse transcriptase polymerase chain reaction test on nasal or throat swab samples of suspected patients to test for Covid-19. The RT-PCR tests look for the presence of the virus in the DNA. They can take anywhere between 12-24 hours to show results.

In comparison, the rapid antibody tests identify disease-fighting antibodies in blood samples and can deliver results in 45 minutes to two hours. However, since antibodies are usually detectable only after around 7-10 days of being infected by the virus, such tests could throw up false negatives – an infected person may appear normal in the blood test.

To avoid such false negatives, the Indian Council of Medical Research, which is overseeing the country’s testing regime, has asked both government and private laboratories to stick to RT-PCR tests for diagnostic purposes.

But in a press statement on Sunday, the Kerala government claimed the ICMR had approved its plans to use rapid antibody kits. “We have got permission to do these tests,” the release said. “We will use ICMR-NIV [National Institute of Virology] approved kits.”

Nivedita Gupta, senior scientist at ICMR, flatly denied this. “The ICMR has not given a go-ahead. They should not be doing this,” she said. Kerala had not even made a formal request asking for approval to do antibody tests, she added.

‘Screening test’

Is Kerala then breaking ranks and devising its own testing strategy? With 214 positive cases until Monday, the state has the second highest number of Covid-19 cases among Indian states.

The press statement by Kerala government said the rapid antibody kits would be used for a “screening test” to identify and isolate suspected carriers, who would subsequently be subjected to an RT-PCR test if the situation warranted.

Public health experts said there was no harm in this approach. “If a state is willing to do, why not?” said Yogesh Jain, a physician and founder of the Jan Swasthya Sahyog in Chhattisgarh. “It does not require much technology, all the district hospitals, even the community health centres can do it.”

Gagandeep Kang, a clinical scientist who heads the Translational Health Science and Technology Institute, an autonomous government institute, tended to agree.

While antibody tests were particularly effective in finding out if a person who had never shown symptoms had been previously infected by the virus, they could also help in the diagnosis of active cases, she said.

She explained: “The first time you get an infection, you make an antibody called IgM, and then after a few weeks it switched to an antibody called IgD. If you find IgM, that means the person is recently infected. In fact, for many infections, we actually make the diagnosis looking at IgM antibodies.”

Test, but what kits?

But how will Kerala source kits for these rapid tests?

So far, India’s drug standards organisation has approved the sale of 18 diagnostic kits made by private companies for Covid-19 testing. All 18 kits are for RT-PCR tests, VG Somani, the Drug Controller General of India, told

But what about the 12 rapid antibody kits approved for an ICMR study? The ICMR has recently ordered 10 lakh antibody testing kits to conduct a research survey which would look for antibodies in the blood samples of asymptomatic individuals across India to gauge the spread of the disease.

Could states also use these 12 rapid antibody kits? “I cannot say that they cannot use it as such,” said Somani, “but there is a testing protocol that the ICMR has put in place, so everyone should be kept in the loop.”

Asked about Kerala’s announcement, he said: “There is often confusion during a crisis. Some states want to do things on their own out of nationalistic sentiments. It is not right to just use antibody kits just like that.”

‘No specific directions’

The Kerala government, for its part, has not disclosed details of where it will source the kits from.

Amar Fettle, the state nodal officer for public health emergencies, said plans were afoot to start rapid testing, but specific directions had not been issued yet. “As of today, we are following what the ICMR has said and doing RT-PCR tests,” he said.

Fettle said he was not aware whether the ICMR had been approached by the state government.

V Meenakshi, the state additional director of public health, also claimed ignorance. “We have not begun these tests yet,” she said. The decision to use antibody tests had been taken at the “secretary level”, she added.

Ranjan K Khobragade, the state health secretary, declined comment, asking this reporter to refer to the chief minister’s daily bulletin. Questions sent over messages to Khobragade and his deputy, Ratan Khelkar, the national health mission director in Kerala, went unanswered.

The story will be updated if they respond.