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Explained: To do rapid tests, or not to

The Indian Council of Medical Research on Tuesday advised states not to use rapid test kits for the next two days, saying it would issue an advisory after their teams carry out field validation of these equipment.

Written by Abantika Ghosh | New Delhi |
Updated: April 21, 2020 6:38:41 pm
Explained: To do rapid tests, or not to A blood sample collected for COVID-19 test in Lviv, Ukraine, earlier this week. (Reuters Photo)

Amid the growth of cases of novel coronavirus disease (COVID-19), states have started to look at “rapid tests” — serological or blood tests — as an alternative to the longer, swab-based tests routinely being used. On Tuesday, the Indian Council of Medical Research on Tuesday advised states not to use rapid test kits for the next two days, saying it would issue an advisory after their teams carry out field validation of these equipment.

At the daily briefing, ICMR’s Dr Raman R Gangakhedkar was asked about the faulty rapid testing kits. “We have received complaint from a state yesterday and so far discussed with three states. Too much variations have been reported in results of rapid test kits and RT-PCR kits. We advise states not to use them for the next two days,” he said.

“These kits will be tested and validated in the field by our teams. We will issue a clear-cut advisory in two day. If problems are detected in batches, we will tell the companies for replacement,” he said.

Coronavirus: What is a serological test?

According to the Johns Hopkins Bloomberg School of Public Health, “Serology tests are blood-based tests that can be used to identify whether people have been exposed to a particular pathogen. Serology-based tests analyse the serum component of whole blood. The serum includes antibodies to specific components of pathogens, called antigens. These antigens are recognized by the immune system as foreign and are targeted by the immune response.”

Blood has two components, a matrix called plasma and the blood cells. The plasma minus the components of whole blood that cause it to clot is known as serum.

How is it different from the tests being done more widely?

The standard test for COVID-19 so far has been the Polymerase Chain Reaction (PCR). It is done after taking nasal or throat swabs of the patient, from which RNA is extracted and converted to DNA, which is then amplified before being checked for confirmation of the virus. The PCR test takes up to nine hours. The long time is also because the swab is first screened to decide the family of the virus; if that confirms it is a coronavirus, a second test is done to ascertain if it is indeed the novel coronavirus SARS-CoV2.

Also read | Whom to test, and when?

The serological test screens the plasma for antibodies that the body develops against the virus. It takes less than 30 minutes. It is important to note, however, that the PCR test is capable of identifying infection at an earlier stage. Only after the antibodies have developed, which takes several days, can the serological test come in. And even for serological tests, the positives will have to go through the PCR filter.

novel coronavirus cases, ICMR, coronavirus test in India, coronavirus patients, community transmission, local transmission, indian express news Coronavirus testing: At the National Institute of Virology in Pune, where final confirmatory tests are done for novel coronavirus infection. (Express Photo: Pavan Khengre)

Which states have been pushing for it?

Kerala has started using the test, with approval from the ICMR. During videoconferencing in the first week of April, Chief Minister Pinarayi Vijayan urged the Prime Minister for central assistance for bringing test kits from Hong Kong. Haryana CM M L Khattar too called for rapid tests, while Maharashtra has got permission to conduct these, reports from Mumbai said quoting state Health Minister Rajesh Tope.

Chhattisgarh Health Minister T S Singh Deo had also tweeted: “Requesting the Central Govt & @drharshvardhan to ensure that @ICMRDELHI formulates comprehensive guidelines for use and purchase of Rapid Tests for #COVID19 as these tests have been used effectively across the world and are needed for expanding testing capacities.”

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Earlier, the Tamil Nadu government had approached ICMR for permission to follow the ‘South Korea-China model” of rapid tests, but the ICMR had said the real-time PCR (RT-PCR) test is more foolproof.

What did the ICMR say now?

The Indian Council of Medical Research on Tuesday advised states not to use rapid test kits for the next two days, saying it would issue an advisory after their teams carry out field validation of these equipment. At the daily briefing, ICMR’s Dr Raman R Gangakhedkar was asked about the faulty rapid testing kits.

“We have received complaint from a state yesterday and so far discussed with three states. Too much variations have been reported in results of rapid test kits and RT-PCR kits. We advise states not to use them for the next two days,” he said.

“These kits will be tested and validated in the field by our teams. We will issue a clear-cut advisory in two day. If problems are detected in batches, we will tell the companies for replacement,” he said.

Also read | Coronavirus testing in India, elsewhere

What is the South Korea model that Tamil Nadu referred to?

South Korea, which had shot up to the top of the COVID-19 chart in February, has emerged as a success story in its containment aggressively using mass testing, including with serological kits, to reduce the number of cases. The country has managed to contain the virus without the kind of lockdown that several countries including India have now gone into.

While it is testing that has got it global praise, it is also a fact that South Korea’s success was as much because of its hospital infrastructure that was ramped up during the earlier outbreaks of SARS and MERS. Even in Daegu, where the country’s 31st patient became an index for some 1,100 contacts, hospitals were clogged but hospitalisation rates remained high.

Though South Korea has become the benchmark, it was Singapore that first started using such tests.

Here’s a quick Coronavirus guide from Express Explained to keep you updated: What can cause a COVID-19 patient to relapse after recovery? | COVID-19 lockdown has cleaned up the air, but this may not be good news. Here’s why | Can alternative medicine work against the coronavirus? | A five-minute test for COVID-19 has been readied, India may get it too | How India is building up defence during lockdown | Why only a fraction of those with coronavirus suffer acutely | How do healthcare workers protect themselves from getting infected? | What does it take to set up isolation wards?

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