The much-awaited Rapid Testing Kits, or RTKs, which use antibody-based blood tests for Covid-19, arrived in New Delhi at 11.30am on Thursday after missing their third deadline by a day, and will likely be used to test for coronavirus disease in areas with no or few cases — the health ministry’s green zones — according to an official at the Indian Council of Medical Research (ICMR).

The kits will be used to test people with fever, cough, and shortness of breath in 325 districts that are currently unaffected, starting with those that are in states with a high number of Covid-19 cases, explained the official, who asked not to be named. This will be the first mass testing exercise in these districts.

“Many states have started dedicated fever clinics; and the samples for rapid testing could either be lifted of people visiting those clinics or cases our front-line workers identify after screening,” added this person.

The move will significantly widen testing for Covid-19 in the country, which currently tests around 203 people per million, with most tests restricted to health care workers treating Covid-19 patients, travellers who may have visited countries with a significant number of infections, and people who may have come in contact, directly or indirectly, with an infected person.

Much of the testing is also happening in so-called containment areas which are themselves within hot spot districts with either outbreaks or clusters (called red zones by the health ministry) or districts that are not hot spots but with clusters. There are 170 hot spot districts and 207 other districts with clusters. According to the health ministry, all other districts are in the green zone. There are around 730 districts in India.

ICMR guidelines say antibody test should be run after seven days of illness, as it takes at least five to seven days for antibodies to develop after contracting an infection.

“An antibody test is not suited for diagnostic purposes but it is a useful surveillance tool for epidemiological studies,” said the ICMR official. Put otherwise, it is a quick and easy way to understand the extent to which the disease has spread.

“These kits are not for early diagnosis as their sensitivity and specificity is lower than RT-PCR tests; it can be used for surveillance purposes, to periodically spot disease trends; to collect data on whether there is an old infection in a section of population or if it is a recent infection.

whether the spread is increasing or being successfully contained in places that are termed as hot spots etc,” Dr RR Gangakhedkar, head of epidemiology and communicable diseases at ICMR, said at a news briefing on Thursday.

And since it is cheaper than RT-PCR, it can easily be deployed for mass testing, if required.

The consignment has 500,000 antibody testing kits and 100,000 RNA extraction kits. Of the 500,000, 300,000 are from Guangzhou Wondfo and another 200,000 from Zhuhai Livzon. The RNA extraction kits are supplied by MGI Shenzhen.

The flight carrying the supplies finally landed in Delhi at around 11.30am on Thursday.

After clearing customs, the kits have been moved to ICMR’s main depot at the National Institute of Malaria Research (NIMR) in Dwarka, which is one of the two main ICMR depots where the orders placed with different suppliers are being received and stored in the cold container unit.

“We have created 16 depots across the country for the storage of these kits, from where the supply is distributed regionally. We have just received the kits and the logistics are being worked out at the moment. We can make use of flights and also transport them by road to nearby places,” said the ICMR official.

The stock is being initially distributed to 6 regional depots in Mumbai, Chennai, Kolkata, Dibrugarh, Bhopal, and Hyderabad, and later to other 10 depots. The supplies are likely to depart Delhi by Friday.

According to people familiar with the mater who asked not to be named, India pulled diplomatic strings after the Chinese suppliers missed three deadlines.

Demand for the RTKs, which some countries hope to be able to use to decide who is immune and can therefore return to work, has soared. And the Chinese government has tightened its export policies after a large number of kits failing quality tests in other countries, causing some amount of embarrassment to Beijing.

“We have been emphasising on having the National Medical Product Administration, China, approval for all items being imported from China. It’s a sort of quality assurance certificate from the Chinese government, and we are rejecting anything that is not certified ,” a second ICMR official said on condition of anonymity.

The Indian embassy in Beijing tweeted that “it is important to ensure product quality as well as reasonable and stable prices”. It called on China’s National Medical Products Administration to expedite registration of Chinese firms, especially those with export orders and already licenced by Indian regulatory bodies.

The external affairs ministry is also working to obtain testing kits from other countries. “Firm quotations have been obtained from companies in Canada, France, Malaysia, the UK and the US. We have also obtained leads from companies in Germany and Japan,” an official familiar with the development said on condition of anonymity.

Experts say that India’s decision to introduce antibody testing kits could be a game-changer in its fight against Covid-19.

“Rapid testing needs to be ramped up for the country to be able to get back to normalcy. If we want to cover maximum people who have symptoms to know the disease burden, then rapid testing is the solution as it is quicker and cheaper, and helps in achieving the ultimate goal of public health care testing,” said Dr T Jacob John, former head of virology department, Christian Medical College, Vellore, Tamil Nadu.

“However, the quality of kits plays a crucial role. It is also a good way of picking infections when we know most of those infected will not show symptoms or depict mild symptoms,” he added.