Global Statistics

All countries
179,698,451
Confirmed
Updated on June 22, 2021 7:03 pm
All countries
162,673,397
Recovered
Updated on June 22, 2021 7:03 pm
All countries
3,891,365
Deaths
Updated on June 22, 2021 7:03 pm

Global Statistics

All countries
179,698,451
Confirmed
Updated on June 22, 2021 7:03 pm
All countries
162,673,397
Recovered
Updated on June 22, 2021 7:03 pm
All countries
3,891,365
Deaths
Updated on June 22, 2021 7:03 pm

False Positive Test: Why do some tests for COVID-19 give false results and how common is ‘false positive’?


Adelaide
Two COVID-19 cases, previously linked to the current outbreak of coronavirus in Melbourne, are now incorrectly classified as positive (infected). These cases are not included in the official Victoria figures, while many risk sites linked to these cases have also been removed.

The main and “gold standard” test to identify the SARS-CoV-2 virus responsible for COVID-19 is the reverse transcriptase polymerase chain reaction (RT-PCR) test. The RT-PCR probe is highly specific. This means that if someone is not really infected, there is a high chance that the test results
will be negative. This test is also very sensitive. So if someone is really infected with the virus, then there is a high chance that the test result will come back positive.

But even though the test is highly specific, there is a slight apprehension that even if a person does not have the infection, he will still show positive in the test result. it’false positive It is called.’ To understand this, it is first necessary to know how the RT-PCR test works. Most people have heard about the PCR test in the Kovid era, but how it works is still somewhat of a mystery.


In an attempt to understand in simple and short words, chemicals are used to extract RNA (ribonucleic acid, a type of genetic material) from swab samples taken from the nose or throat. This includes the normal RNA of a person and if the SARS-CoV-2 virus is present then its RNA.

This RNA is then converted into DNA (deoxyribonucleic acid) – this is called ‘reverse transcriptase (RT)’. Small segments of DNA are amplified to detect the virus. With the help of a special type of fluorescent dye, a test is identified as negative or positive based on the brightness of the light after 35 or more addition cycles.

The main reason behind why false positive results come up is a laboratory error and off-target reaction, i.e. the test cross-reacted with something that is not SARS-CoV-2.


Laboratory errors include clerical errors, testing the wrong sample, contamination of another sample with another’s positive sample, or problems with the reactants used (such as chemicals, enzymes, and dyes). Those who have had Kovid-19 and have recovered, sometimes they also appear infected on examination.

To understand how common such false results are, we have to look at the false positive rate, i.e. the ratio of people who were tested and found positive despite not being infected. The authors of a recent preprint (a paper that has not been reviewed or independently validated by other researchers) reviewed the evidence on false-positive rates for RT-PCR testing.

They combined the results of several studies and found the rate to be 0-16.7 percent. In 50 percent of these studies, this rate was found to range from 0.8-4.0 percent. A systematic review on false negative rates in RT-PCR tests found the false negative rate to be 1.8-5.8 percent. However, the review recognized that the quality of most studies was poor.


According to the author of this article, no test is perfect. For example, if the rate of false positive in the RT-PCR test is assumed to be four percent, then for every 1,00,00 people who are found negative in the test and who do not have true infection, 4,000 will come falsely positive. can. The problem is that we will never know about most of these. The person found infected will be asked to live in isolation and every person who comes in contact with him will assume that he has a disease without symptoms.

Any person who is said to be infected due to wrong test is forced to live in isolation. It is very stressful if someone is told that you have a fatal disease, especially for the elderly as their health is already fraught with risks. Similarly false negative results are obviously very worrying as it can be dangerous for infected people to move freely in the community.

Overall, it should be said that both false negative or false positive results are going to cause problems.

Fake report of RTPCR was reported, Minister Subodh Uniyal did surprise inspection

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