Antibody tests start in Delhi’s Nabi Karim, all 62 results negative

A negative result doesn’t conclusively show that a person is free of the disease, as antibodies are not present in a patient’s bloodstream in the initial stages of the infection.

Delhi rolled out antibody testing for coronavirus disease (Covid-19) in the central district’s Nabi Karim containment zone on Monday, two days after the government in the city-state received 42,000 rapid diagnostic kits that can return results within 30 minutes.

Delhi rolled out antibody testing for coronavirus disease (Covid-19) (AP)

All 62 people tested in the containment zone were negative for antibodies of the disease. A negative result doesn’t conclusively show that a person is free of the disease, as antibodies are not present in a patient’s bloodstream in the initial stages of the infection.

While Delhi health minister Satyendar Jain said on Saturday that the government planned to deploy the kits in containment zones of all districts simultaneously, 10 of them were still “waiting for protocols” to start rapid testing on Monday, according to an official.

All 11 revenue districts have been declared Covid-19 hot spots, with the tally of containment areas across the city rising to 84 with five new “red zones” on Monday.

“We started rapid testing in Nabi Karim today and the good thing is all the 62 people who were tested did not show a positive result,” said Nidhi Shrivastava, district magistrate (Central Delhi).

“Our team conducts surveys in the containment zones daily. We ask people whether they have had fever and cough in the last five or six days. If yes, we ask them to come to the centre with us and get tested,” a Central District official said on condition of anonymity. The district also plans to deploy a mobile testing van to reach the community and increase sample collection.

On Thursday, India received a batch of 550,000 rapid testing kits (RTKs) from China after two deadlines for the shipment were missed. The Indian Council of Medical Research says that RTKs are not meant for diagnosis but should ideally be used for surveillance purposes to establish trends. The apex body for biomedical research recently revised guidelines after states appealed that they be allowed to use RTKs in hot spots so that containment efforts can be stepped up accordingly.

Those who are found positive in the test must be quarantined for at least seven days. Those who test negative should also remain under home quarantine for at least seven days if they are in hot spots. “We suggest quarantine even for those who do not test positive because the fear is they might not have developed the antibodies when we tested,” an official from Delhi’s health department said, asking not to be named.

The samples for RT-PCR tests are collected at designated centres – the Delhi government has set up 22 such centres at hotels and dharamshalas for community testing. The rapid tests will also be conducted here by laboratory technicians from dispensaries in the area.

According to the health department’s guidelines, the health care workers collecting the samples have to wear a full personal protective equipment (PPE) kit.

The rapid testing kits, which look like home pregnancy tests, use a skin prick to draw blood for diagnosis. Only those with influenza-like symptoms – fever, cough and cold – are currently being tested.

The 42,000 RTKs procured by Delhi so far will be deployed only in containment zones. “The government is not yet in a position to conduct random testing of symptomatic individuals because of resource constraints,” said Delhi health minister Satyendar Jain.

Delhi plans to test 60,000 people by the end of the month using RTKs. The government has also placed an additional order for 50,000 kits from an ICMR-approved vendor.

While the Central District was the first to roll out RTKs for community testing, Shashi Kaushal, district magistrate (North-East), said: “The kits have arrived at the district store but we are waiting for a clear protocol on how to conduct the tests – from collection of samples to assessment of results.”

On Monday, the Delhi government used RTKs to evaluate 92 cured Covid-19 patients, being discharged from Lok Nayak hospital, so that they could be considered for plasma therapy trials. Plasma therapy uses one of the blood components rich in the virus-fighting antibodies in people who have recovered from Covid-19 to help critical patients fight the virus better.

“The plasma is diluted 1:1, then 1:2, then 1:3, just to check till what level of dilution the sample comes out positive. The solutions that test positive at the highest level of dilution are the ones with high antibody levels. Ideally, a neutralising antibody test must be done where the antibody is added to a viral culture to check its effect, but that can only be done in BSL III laboratories. This is recommended as the best practice the world over in the absence of the other test,” said Dr SK Sarin, director, Institute of Liver and Biliary Sciences (ILBS). To test the antibody level of each person, 10-20 RTKs are needed.