RT-PCR test: False positive and False-negative reports explained in detail

As the world fights the COVID-19 pandemic, we face the challenge of developing reliable methods for identifying people infected with the SARS-CoV-2 virus. The importance of having safe and easily accessible testing to screen for Covid-19 disease has grown exponentially in recent months. Although Test availability has been a major concern, test accuracy might prove to be a more serious long-term issue. Although RT-PCR testing is considered a very reliable testing procedure the precision of antibody testing and RT-PCR is insufficient to meet the demand for a high number of screening tests. False-negative RT-PCR results and false-positive antibody testing are both problematic.

What is the RT-PCR test?

The RT-PCR Test is also called a real-time reverse transcription-polymerase chain reaction test. It is a molecular test that is highly used for the detection of the SARS-CoV-2 virus in the body. The Covid RT-PCR Test is used for the detection of nucleic acid from SARS-CoV-2 by collecting nasopharyngeal or oropharyngeal swab specimens from individuals suspected of COVID-19.

How does it work?

RT-PCR test involves reverse transcription (RT) of viral RNA into DNA and then this Complementary DNA is amplified by the help of another method called polymerase chain reaction (PCR). It helps to detect even a very low amount of virus at the time by amplification of DNA even when symptoms of the disease are not noticeable.

How accurate are the RT-PCR tests?

RT-PCR is considered as the gold standard for detecting COVID-19. It’s one of the quickest and most accurate COVID-19 detection procedures available. Real-time reverse transcription polymerase chain reaction (RT–PCR) is highly sensitive and it can deliver a reliable diagnosis in 6 hour. Many companies have emerged to provide RT-PCR testing for covid-19 at an affordable price. SpiceHealth has emerged as the fastest growing diagnostic lab in India having conducted more than 2.3 million RT-PCR tests since its launch in Delhi in November 2020.SpiceHealth’sRT-PCR tests in Delhiare the country’s cheapest Covid RT-PCR test starting from just Rs. 499/-. SpiceHealth uses high quality gear and trained expertise to generate reliable results. Book a test now.

What does RT-PCR results indicate?

  • Positive results are indicative of active infection. If your test is positive, take all the required steps, consult a doctor, stay home and isolate yourself from others.
  • Negative results interpret that RNA Specific to SARS-COV-2 is not detected.  If your test is negative, continue to take preventive measures to protect yourself from getting COVID-19.
  • Inconclusive results indicate the case of clinical suspicion and a repeat Sample is suggested.
  • A Non Diagnostic result means that internal control not detected, samples need to be repeated


What are the errors that can arise during RT-PCR testing?

Despite the fact that the RT-PCR test has become the gold standard for detecting SARS-CoV-2 infection, Absolute certainty in diagnosis is impossible to achieve. There are two kinds of errors that can arise during covid-19 testing.

  • false positive 
  • false negative 

There is no diagnostic procedure with 100% sensitivity and specificity. false-negative rates have been observed.

False Positive

A false positive is an error in which a test result incorrectly indicates the presence of a disease when the disease is not present. The Covid RT-PCR test is very unlikely to return a false positive. If the test comes out to be positive, we can be sure that it has correctly detected genetic material from the SARS-CoV-2 virus, and thus the patient is suffering from Covid-19 disease

False negatives

A false negative error occurs when a person has a specific disease but the diagnostic test for that disease fails to detect it.  There is no diagnostic procedure with 100% sensitivity and specificity. Despite the fact that the RT-PCR test has become the gold standard for detecting SARS-CoV-2 infection, false-negative rates have been observed

What could be the reasons for false negative results?

The false negative error could occur for a variety of reasons.

  • People may obtain a negative Covid-19 test result but be infected with the virus if they get tested either too early or too late.  Normally, Covid-19 manifests effectively by the fifth day of an infection cycle. Thus, viral loads are often higher one to three days before the onset of symptoms, or when the symptoms are actually seen. Thus ,If the sample was not taken at the proper time during the infection, false negative test findings can be arise
  • False negative results can also arise due to mutations. To detect the presence of a viral gene, the RTR-PCR test targets a specific area or areas of one or more viral genes. If a mutation occurs in the segment of the genetic material being tested, a test may produce false negative results. Mutations are less probable to fool tests that use multiple genetic targets, such as those used in India. Certain mutants have emerged, leading to a controversy that it is now known to target the lung by bypassing the upper respiratory tract — a situation that could rule out an Covid RT-PCR test based on nasal cavity and throat samples.
  • Since there was a rapid surge in the capacityof the Covid RT-PCR test, it’s likely that the positive and negative results in the laboratory were mixed together. Proper protocols, on the other hand, are followed during testing procedures. And the chances of this happening remain slim.
  • Bad sample collection can also be a reason for the wrong results. It is also suggested that random quality checks and surveillance of these testing kits be performed to ensure that the tests work.

Why is it important to know about the errors in RT-PCR testing?

It is crucial to be aware of the false positive and false negative reports. Infected people who have false negative RT-PCR results may not be isolated and can spread the virus to others.  False positive results can make patients and clinicians nervous. Furthermore, unnecessarily isolating large groups of people wastes both human and material resources.