How new coronavirus mutants are fooling RT-PCR tests

As India battles the raging COVID-19 pandemic, several patients are getting tested for the deadly disease. However, the variants of novel coronavirus are making it difficult for RT-PCR tests to give the correct results in one go. These incidents are becoming more common during the second wave in India.

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According to a Times Of India report, doctors are witnessing cases where patients have typical symptoms of COVID-19 but their test report comes back negative. So they need multiple RT-PCR tests to detect the virus. Notably, RT-PCR (Reverse Transcription Polymerase Chain Reaction) test is considered to have a high specificity rate and gives fewer false results.

“All such persons who tested negative through conventional COVID-19 testing methods but had disease symptoms, came positive in the lavage test,” Dr Aashish Chaudhry, the managing director of Aakash Healthcare, told TOI.

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How the coronavirus variants are fooling COVID-19 tests

A paper, ‘Mutations on COVID-19 diagnostic targets’, published by the University of Illinois and Michigan State University, says that the virus was already changed enough by September. This was the time when the coronavirus variants found in Brazil, United Kingdom and South Africa were not even detected.

The paper added that PCR tests were developed on early clinical specimens containing a full spectrum of SARS-CoV-2. Mutations “will cause a large number of false positive and false negative tests if currently used diagnostic reagents are undermined,” the scientists warned.

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The US Food and Drug Administration (FDA), too, alerted healthcare workers about the UK variant’s potential to produce false negative results in January this year.

The fears came true after Finland and France faced the problem of false negatives in February and March.

Why only some patients suffer from this problem

There is a possibility that some people do not develop a nasal and throat cavity due to the virus, which leads to the failure of swab tests. “Swab samples that were taken from these areas did not yield positive results,” Dr Pratibha Kale, associate professor of clinical microbiology at the Institute of Liver and Biliary Sciences, told TOI.

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Dr Vivek Nangia, the chief of the pulmonology division at Max Healthcare, told TOI that 15-20% of COVID patients experience this problem. “They are highly symptomatic of the disease but test negative. This is a serious problem because such patients can continue to spread the infection if they are admitted in non-Covid areas. Also, it can delay the treatment,” he said.