The Indian Council of Medical Research has advised antibody tests in areas that are emerging as hot spots of Covid-19. (HT Photo)

The Indian Council of Medical Research (ICMR) advised on Thursday antibody tests (or blood tests) in areas that are emerging as hot spots of the coronavirus disease (Covid-19), a move that will ensure faster detection of all possible cases in these clusters and help authorities buy some precious time to contain the fast-spreading pandemic.

The test used now --- PCR (polymerase chain reaction) --- identifies the Sars-CoV-2 virus from throat of nasal swab samples of people with symptoms or high-risk individuals (health workers and family members) who might have come in contact with a Covid-19 patient.

The antibody detection blood test will identify people who already have been infected, but have mild or no symptoms, according to experts who say the move will help us know how many have been able to fight off the infection and have become what could be called a “corona-blocker”.

While the results of PCR tests take up to five hours, the antibody test results will be available in 15-30 minutes.

“Population in hotspot areas may be tested using rapid antibody test. And antibody positives to be confirmed by RT-PCR (reverse transcription-PCR) using throat/nasal swab, and antibody negatives to be quarantined at home,” said the interim ICMR advisory.

This means positive results will be reconfirmed using the PCR test.

The antibody test uses a few drops of blood to determine whether a person has antibodies against the coronavirus. Antibodies in the immune system means the person had the disease at some point in the past, even though the person was never tested for it, and has now recovered.

An ICMR official, who spoke on the condition of anonymity said, the move will mean getting quicker results even if there is a large number of people.

“However, to ensure there are no false positives or false negatives, we recommend confirmatory PCR-based test for all positive results,” this official said.

The ICMR also released a link (www.finddx.org/) having an information on all available CE-marked rapid SARS-CoV-2 antibody tests. CE-In Vitro Diagnostic approved kits can be used directly after due approval from Drugs Controller General of India (DCGI) and intimation to ICMR.

ICMR earlier made public an expression of interest to procure a million anti-body testing kits from manufacturers across the globe. However, due to the shortage of supply, the number was revised to 500,000 testing kits. The first shipment is expected by this weekend (April 5).

Experts say that India’s decision to introduce anti-body testing kits could be a game.

“These tests are expected to be very economical, simple and give results within 15-20 minutes. They are being used for contact-tracing in some countries. The Indian health system has lot of experience in doing such tests, like the ones for dengue and chikungunya. So it will be easy to ramp up the screening. It is also a great tool for surveillance, and building up epidemiological data. Indian companies would be able to produce them easily and at massive scale,” Lalit Kant, a senior infectious disease expert, said.

Kant also had a word of caution. “While using these tests, one has to be careful about false positives as there may be cross-reaction with other virus antigens. Antibodies take time to develop, so if the test is performed early in the phase of the infection, may not give correct results. This decision is transformational,” he said.

But he pointed out that the move would ease workload off main laboratories, as sophisticated equipment or highly trained manpower would not be needed for the process.

“Mass screenings can be done using these tests to give us vital information on the number of people infected who never went to the hospital. It would give us an idea of the denominator to calculate fatality ratios,” he said.

On Thursday, the Union health ministry said it identified 20 existing and 22 potential hotspots in the country, and asserted that although there was no evidence of widespread community transmission, containment measures will require large human resources.

The advisory stressed capacity building, saying identified human resource needs to be trained online in areas such as field surveillance, contact tracing, packaging and shipment of specimen and hospital infection prevention and control, including use of appropriate personal protective equipment.