RT-PCR coronavirus tests and false negatives: Why is that going down?


Earlier this month, Arjun Sharma (name changed on request) visited three hospitals in Delhi with his father, trying to receive an oxygen bed for him. His father had tested negative for Covid-19 on an RT-PCR test, but was once showing symptoms of the disease–his oxygen levels had dropped and a CT scan showed infection and pneumonia in his lungs.

“Doctors who we consulted said that my father most likely has Covid-19 and will have to get admitted to a hospital to receive oxygen improve. But the test was once negative despite his serious symptoms, and perhaps this was once a false-negative test result,” said Sharma, a central government employee living in east Delhi.

All three hospitals which Sharma visited with his father were unwilling to confess him. They told him that whether his father was once Covid-19 positive, they could try to accommodate but since his test had shown up negative, they could not offer him a bed as they were keeping their beds only for those testing positive for Covid-19.

After several days of struggling, and taking the assistance of other civil society volunteers in Delhi, Sharma has admitted his father to a government-run hospital in east Delhi where his father has been on oxygen improve since April 25.

Questions have been raised on if the RT-PCR test, while fundamental for accuracy in Covid-19 detection, is returning false negatives, and this has more recently been blamed on the test’s purported inability to detect new Covid variants. People who find themselves getting tested may show symptoms of Covid-19 although their tests give negative results. In other cases, people are unable to receive tested because of the scarcity of testing kits in different parts of the country, but are showing Covid-19 symptoms. Either way, the gate-keeping of the RT-PCR test is proving cumbersome for plenty of to navigate.

On April 23, the Delhi government issued an order acknowledging that people with RT-PCR negative tests for Covid-19 were being denied admission in Delhi hospitals, despite having symptoms. “No patient requiring medical aid will have to be denied remedy,” said the order.

Experts have long emphasised the want to test people widely, and that even people who find themselves presenting with severe acute respiratory illness or influenza-like illness will have to be tested for Covid-19 since their symptoms are similar.

Other ways to tell whether it is Covid-19

“It is extremely common, not at all infrequent,” for patients to be infected with Covid-19 but for it to not show up on test results, said Kamna Kakkar, senior resident in the intensive care unit, branch of pulmonary and critical care medicine, at Pandit Bhagwat Dayal Sharma Post Graduate Institute of Medical Sciences, Haryana.

“Even supposing the RT-PCR test is a superb test, there could have been problems with how the swab was once taken, if it went deep enough to take the pattern, or whether possibly the person took the test too late and the virus was once no longer in the upper respiratory region but inflammation had settled in within the lungs.” All of this can lead to a negative RT-PCR test, she said.

She said that is why doctors are trained to recognise diseases also by their symptoms and not just lab reports.

Provided the high number of Covid-19 patients and the scarcity of tests, Kakkar says that CT scans and X-rays can also be some proxies, which doctors can rely on while diagnosing for Covid-19 particularly since people are unable to access tests easily.

Then again, she said it is mostly junior doctors who meet patients when they first come to a hospital. “When a person comes with fever and shortness of breath, as a senior resident I realize it can also be quite a lot of things–it could be Covid-19, heart attack, dengue, scrub typhus, chikungunya, even acid reflux. So clinical verdict here is essential, so that you can tell the difference.” But since there are mostly junior doctors on the frontline, and the system is overloaded, administrators have insisted on lab parameters like RT-PCR test results with a purpose to be admitted, she explained.

“What whether we did not have dependable RT-PCR tests for Covid-19, would we not as doctors still have treated people for the disease based on our clinical observations of the disease in a patient?” said Kakkar.

False negatives

A ‘false negative’ in diagnostics parlance is when a person in truth does have a specific disease but the diagnostic test for it fails to detect that disease.

This can happen whether the technology used in the test isn’t accurate, or not particular or touchy enough to select up that disease. It can also happen because the technician performing the test did not conduct it properly, or the reagents used are of bad quality. Infrequently even supposing the technology is fine and the pattern was once taken accurately, the pattern could have been transported under inappropriate conditions to a lab.

And, as we said before, false negative test results can arise whether the pattern was once not taken at the correct time in one’s infection.

Any link to variants?

The Indian government has said that the presence of false negatives could also be not linked to the new SARS-CoV-2 variants. The RT-PCR tests do not overlook the United Kingdom, Brazil, South Africa and double-mutant variants, as the tests being used in India target more than two genes, said a press release from the government on April 16.

The RT-PCR tests for Covid-19 look out for the presence of three genes on the SARS-CoV-2 virus. These genes have not changed much and thus the RT-PCR tests which are already in use, are ready to identify these genes and give positive results, said Shahid Jameel, director of Trivedi School of Biosciences, Ashoka University. “The new variants which scientists are studying don’t seem to be likely to drastically have an effect on the ability of RT-PCR tests to give positive results for Covid-19,” he said.

With the intention to check if tests work, he said there will have to be random quality checks and surveillance of these testing kits.

On this, Arokiaswamy Velumani, chairperson of Thyrocare, a large diagnostics chain in India, said that he too isn’t worried approximately RT-PCR tests not doing an accurate job for Covid-19. “The government has asked us to send 10 positive and negative samples each month to designated government labs where our test results are verified… This can be a continual monitoring of the quality of these tests to be sure that they’re accurate and we are testing accurately,” he said.

When to receive tested?

One more reason why people may get a negative Covid-19 test result, but may in truth be positive for the virus, is whether they test too early or too late in their infection. But when is the correct time to receive tested?

A few of the many resources that the World Health Association (WHO) has shared on testing for Covid-19, there is not any particular guidance on when to receive tested. IndiaSpend contacted the WHO with queries, and a spokesperson explained the following over email: RT-PCR tests are in most cases “highly accurate” but “lower viral loads may increase the likelihood of false negative results”.

When is a viral load of the SARS-CoV-2 virus likely to be low? On this, the spokesperson said that viral loads are in most cases high one to three days before the onset of symptoms, or at the time when symptoms begin, and in the early days of illness for gentle patients (five to seven days), and maybe longer for severe patients.

“There’s no set timing on when a person will have to be tested, with the exception of with regards to whether they develop symptoms. Whether a person develops symptoms, they will have to be tested as soon as conceivable,” they said. Since symptoms “may develop in hours to days after exposure”, they said, “there is not any particular set time for testing”.

Simply put, one will have to use their discretion and get tested at the soonest, whether one has been in definite proximity with someone who has tested positive for Covid-19 or whether one has started to show symptoms, and will have to not wait until symptoms intensify.

What approximately near contacts? On this, the WHO says there is not any need for all contacts to be tested but they will have to be quarantined, and whether these contacts remain without symptoms, they may be able to be tested “as capacity allows”.

In sum, “a negative test result does not make it possible for the person will not go on to develop Covid-19 in the remaining days of the incubation period”, the spokesperson said. False-negatives could be because of “bad sampling or processing”, they said, adding that when health systems are stressed, “the chances of human error may understandably increase”.

The Indian government issued testing strategy documents, which it has up to date once in a while, but not since May 2020. An advisory to states based on this strategy was once issued in September 2020. Both these documents did not specify when in a person’s infection they will have to get tested.

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