how RT.PCR give false test of corona virus

false negative' in diagnostics parlance is when a person actually does have a particular disease but the diagnostic test for it fails to detect that disease.


This can happen if the technology used in the test is not accurate, or not specific or sensitive enough to pick up that disease. It can also happen because the technician performing the test did not conduct it properly, or the reagents used are of poor quality. Sometimes even if the technology is fine and the sample was taken correctly, the sample could have been transported under inappropriate conditions to a lab.


And, as we said before, false negative test results can occur if the sample was not 







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

By Anoo Bhuyan | IndiaSpend | Last Updated at May 01 2021 14:53 IST

Topics Coronavirus | Coronavirus Tests | Coronavirus Vaccine

 

 

 

 

 





A health official takes a swab sample of a child who returned from Pakistan at a Covid-19 coronavirus testing centre in Srinagar

Earlier this month, Arjun Sharma (name changed on request) visited three hospitals in Delhi with his father, trying to get an oxygen bed for him. His father had tested negative for Covid-19 on an RT-PCR test, but was 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 should get admitted to a hospital to get oxygen support. But the test was negative despite his serious symptoms, and maybe this was 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 admit him. They told him that if his father was 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 help 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 support since April 25.


Questions have been raised on whether the RT-PCR test, while essential 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 are getting tested may show symptoms of Covid-19 even though their tests give negative results. In other cases, people are unable to get tested due to the shortage 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 many 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 should be denied treatment," said the order.


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


Other ways to tell if it is Covid-19


"It is very common, not at all rare," 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, department of pulmonary and critical care medicine, at Pandit Bhagwat Dayal Sharma Post Graduate Institute of Medical Sciences, Haryana.


"Even though the RT-PCR test is a good test, there could have been problems with how the swab was taken, whether it went deep enough to take the sample, or if perhaps the person took the test too late and the virus was no longer in the upper respiratory region but inflammation had settled in inside the lungs." All of this can result in a negative RT-PCR test, she said.


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


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


However, 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 know it can be a number of things--it could be Covid-19, heart attack, dengue, scrub typhus, chikungunya, even acid reflux. So clinical judgement here is very important, to be able to 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