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Explained: Different types of coronavirus tests & how effective they are?

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NEW DELHI: In the wake of the coronavirus pandemic, a number of medical terminologies like rapid antibodies test and RT-PCR test have come into focus.

However, right now, there is no one Covid test which is fully accurate. False-negatives are always possible. While RT-PCR is considered the gold standard for testing, researchers are developing novel testing kits that are faster and more accurate than RT-PCR.

Here is all you need to know:

COVID TESTING IN INDIA

RT-PCR test & how it is done

A reverse transcription polymerase chain reaction (RT-PCR) test is a laboratory technique combining reverse transcription of RNA into DNA that detects the virus while the antibody tests, which use blood, detect the body’s response to the virus, experts said.

The World Health Organization and the US Centers for Disease Control and Prevention considers PCR tests the “gold standard” of Covid-19 testing, but, like all tests, they’re not perfect.

The sample is placed in a PCR machine, which uses cycles of heating and cooling to help ‘reagents’ amplify the target DNA into millions of copies. A fluorescent dye is added — the dye glows if the result is positive. In lab conditions, RT-PCR is almost 100% accurate.

RT-PCR tests take time and are a costly affair because of its elaborate kit.

In government labs, the tests are free but at private laboratories, which use RT-PCR test the cost is Rs 4,500.

Rapid Antibodies Test

Unlike other tests, antibody tests aren’t meant to pick up on the current infection with SARS-CoV-2. The antibody tests look for SARS-CoV-2-specific antibodies to see if you’ve previously had coronavirus.

Also termed as immunity tests, a positive test could mean a person has been exposed to the virus.

“The rapid antibodies tests are less expensive and the results can come in 20-30 minutes. It essentially tests if the antibodies in response to the coronavirus infection have been generated or not,” said Delhi-based lung surgeon Arvind Kumar.

Rapid antibody tests are part of a measure introduced by the Indian Council of Medical Research’s immunity certificate program and used in serosurveys to map out Covid exposure in towns and cities.

TESTING TYPES IN THE US

There are three broad categories of coronavirus tests in the US Two diagnose whether you have an active infection, and a third indicates if you previously had the virus.

Genetic tests

Most tests look for bits of the virus’ genetic material, and require a nasal swab that is taken by a health professional and then sent to a lab. This is considered the most accurate way to diagnose an infection, but it’s not perfect: The swab has to get a good enough sample so any virus can be detected.

These tests usually take hours to process at the lab so you likely won’t get results back for at least a day, though a handful of rapid tests take about 15 minutes on site. Other genetic tests use saliva, instead of a swab.

Antigen tests

A newer type of test looks for proteins found on the surface of the coronavirus, rather than the virus itself. These antigen tests are just hitting the market, and experts hope they’ll help expand testing and speed up results.

Antigen tests aren’t as accurate as genetic tests, but are cheaper, faster and require less specialized laboratory equipment. They still require a nasal swab by a health professional.

Using samples from the nose or throat, an antigen test can identify positive cases in minutes but isn’t as accurate as RT-PCR, which searches for genetic material of the virus.

But it can be used to screen people in hospitals and workplaces — any cases it flags would then be followed up with RT-PCR for confirmation.

A recently approved test from Abbott Laboratories takes 15 minutes and can be performed at schools, offices and other locations.

While antigen testing is becoming more common in the US, only a few such tests have been approved by the FDA so far.

Antibody tests

Antibody tests look for proteins that the body makes to fight off infections in a patient’s blood sample. Antibodies are a sign that a person previously had Covid-19.

Scientists don’t yet know if antibodies protect people from another infection, or how long that protection might last. So antibody tests are mostly useful for researchers measuring what portion of the population was infected.

Efficacy of these tests

How well these tests work depends on several factors, including the time from the onset of illness, the concentration of virus in the specimen, the quality of the specimen collected from a person and how it is processed, and the precise formulation of the reagents in the test kits, experts said.

Additionally, false positive results — that is, a test showing that a person is infected when they are not — could occur if the antibodies on the test strip also recognise antigens of viruses other than Covid-19, such as from human coronaviruses that cause the common cold, they said.

(With inputs from agencies)

The Times of India is an Indian English-language daily newspaper owned by The Times Group. It is the third-largest newspaper in India by circulation and largest selling English-language daily in the world. according to Audit Bureau of Circulations.

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INDIA

PM Modi reviews Covid-19 situation with CMs, representatives of 7 states with high caseload

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NEW DELHI: Prime Minister Narendra Modi on Wednesday reviewed the Covid-19 pandemic situation with chief ministers and other representatives of seven high-case-load states through video conference.

The virtual meeting, also attended by health ministers of these states, began in the evening.

These states are Maharashtra, Andhra Pradesh, Karnataka, Uttar Pradesh, Tamil Nadu, Delhi and Punjab, officials said, noting that more than 63 per of the active cases in the country are concentrated in these seven states.

They also account for 65.5 per cent of the total confirmed cases and 77 per cent of the total deaths, a statement had said earlier.

Along with the other five states, Punjab and Delhi have reported an increase in the number of cases being reported recently, they said, adding that Maharashtra, Punjab and Delhi are also reporting high mortality with more than two per cent case fatality rate (CFR).

Other than Punjab and Uttar Pradesh, the case positivity rate of these states has also been observed to be above the national average of 8.52 per cent.

The Centre, as per the statement, has been leading the fight against Covid-19 in effective collaboration and close coordination with the state and union territory governments.

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INDIA

Opposition parties request President Kovind not to give assent to contentious farm bills

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NEW DELHI: Opposition parties have requested President Ram Nath Kovind not to give his assent to the contentious farm bills, and conveyed to him that their passage in Rajya Sabha was “unconstitutional”, Ghulam Nabi Azad said on Wednesday.

The government should have consulted all parties, farmer leaders before bringing the farm bills, Azad said after meeting the President.

“The Constitution was undermined …We have given a representation to President that the farm bills have been passed unconstitutionally and he should return these bills,” Azad said.

The Farmer’s Produce Trade and Commerce (Promotion and Facilitation) Bill, 2020, the Farmers (Empowerment and Protection) Agreement of Price Assurance and Farm Services Bill, 2020 and the Essential Commodities (Amendment) Bill, 2020, have been passed by both Houses and await presidential assent.

There was a ruckus during the passage of two of the three farm bills in Rajya Sabha on Sunday following which eight Opposition MPs were suspended.

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INDIA

10 states, UTs reporting 74 per cent of new Covid-19 cases, 83 per cent of deaths

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NEW DELHI: At least 10 states including Union Territories (UTs) are reporting 74 per cent of newer confirmed Covid-19 cases and 83 per cent of the deaths in the last 24 hours due to coronavirus infection, the Union Health Ministry said on Wednesday.

“A total of 83,347 new cases (active cases) have been reported in the last 24 hours in the country. About 74 per cent of the new confirmed cases are concentrated in 10 states/UTs,” the ministry said in a statement.

According to the ministry, in the last 24 hours, Maharashtra has alone contributed to about 18,390 new cases, while Andhra Pradesh has reported at least 7,553 cases. Karnataka has contributed to 6,974 cases, Uttar Pradesh has witnessed 5,650 cases, Tamil Nadu has reported 5,337 cases, Odisha is contributing to 4,189 cases, Kerala has seen 4,125 cases, while Delhi has reported 3,816 cases. West Bengal has witnessed about 3,182 cases and Chhattisgarh has reported 2,736 cases.

“About 1,085 deaths have been registered in the past 24 hours and 10 states/UTs account for 83 per cent of the deaths in the last 24 hours due to Covid. Maharashtra reported 392 deaths followed by Karnataka and Uttar Pradesh with 83 and 77 deaths, respectively. West Bengal has reported 62 fatality, Tamil Nadu has witnessed 76 deaths, Andhra Pradesh has seen 51 mortality, Punjab has reported 66 deaths, Delhi has witnessed 37 fatality followed by Haryana which has registered 29 deaths while 28 people have succumbed in Chhattisgarh due to the virus in the last 24 hours,” the ministry said.

The Union Health Ministry also informed at least 14 states/UTs have demonstrated better Covid-19 response strategy with higher Tests Per Million (TPM) and commensurate lower positivity rate than the national average.

According to the official data, India’s national cumulative positivity rate is 8.52 per cent and the TPM stands at 48,028 on Wednesday.

India’s testing capacity has surged to more than 12 lakh daily tests. More than 6.6 crore total tests have been conducted across the country so far.

“Nearly 14 states/UTs have demonstrated better Covid response with higher Tests Per Million (TPM) and commensurate lower Positivity Rate than the national average. These include– Mizoram, Manipur, Daman and Diu and Dadar and Nagar Haveli, Arunachal Pradesh, Gujarat, Sikkim, Tripura, Jammu and Kashmir (UT), Odisha, Assam, Punjab, Uttarakhand, Haryana and Andaman and Nicobar Islands,” the ministry said.

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