Jomotshangkha man tests negative for the 3rd time on PCR

Restriction in Jomotshangkha lifted

Younten Tshedup

What could come as a relief to thousands of worried and confused Bhutanese, the 55-year-old Jomotshangkha shopkeeper tested negative for the novel coronavirus, for the third time in a week.

Swab sample of the shopkeeper was sent to the Phuentsholing hospital yesterday after testing negative twice on the reverse transcription polymerase chain reaction (RT-PCR) machine in Mongar. The sample tested negative when tested on RT-PCR machine in Phuentsholing. The result was declared late last night.

He had tested positive for antibody IgM on the rapid diagnostic test on April 30, a test kit designed for testing the antibody-antigen reaction for Covid-19.

Clarifying the confusion surrounding the testing procedures, officials from the health ministry said that while the suspect had tested positive on rapid test, the test did not establish he tested positive for Covid-19.

To confirm if a person is Covid-19 positive or not, the highly specific confirmatory test, RT-PCR is conducted.    

Infection explained

After a person is infected with a virus or bacteria, he or she does not show the symptoms immediately. There is a lag phase (1-2 day) where the pathogen does not multiply. As the pathogen begins multiplying, the body, in its defence starts producing antibodies.

Clinical microbiologist with the national referral hospital, Dr Tshokey, said that normally the first antibodies produced in response to initial infections are the IgM antibodies. He said that the body starts producing a large amount of antibodies (IgM) in response to the infection. Subsequently, the number of virus start declining, as the antibody fights the virus. Usually, by the third week, the number of IgM antibody drops and the body starts producing IgG antibody.

“Between the first week of infection and the third, the rapid diagnostic test is the most effective tool to detect if a person is infected with a virus,” he said.

Dr Tshokey said that the man in Jomotshangkha tested positive for the IgM antibody on the rapid diagnostic test, meaning he was recently exposed to the virus. However, he said that the exposure could have been with any other strain of coronaviruses. The microbiologist said that including the SARS and MERS viruses, there are four common coronaviruses that can infect human. He said that about 20 to 30 percent of the common flu are caused by these common coronaviruses.

To nullify the probability of human error during the test, the suspect was tested seven times on the rapid test and the results were the same, positive for IgM.

Although a highly sensitive test and specific for Covid-19, he said that the rapid test kits have 0.2 percent chances of showing ‘false positive’ results. “This is inherent with all test kits. There is no test in the world that is perfect.”

That is why, he said when a person tests positive on the rapid test, a confirmatory test on the RT-PCR has to be conducted. The RT-PCR identifies the gene of the virus and is highly specific. “If the RT-PCR is positive, then the person definitely has the virus.”

Dr Tshokey, who is a member of the health ministry’s technical advisory group (TAG), said that because there are no means to prove if the test results in Jomotshangkha were false positive or if it was a case of cross-reaction, it was the right decision taken by the government to put the dungkhag under strict restriction for a week.

“The small inconvenience caused to a single person or a community or even a dzongkhag is for the benefit of the whole nation,” he said. “We are taking the most stringent public health measures in our effort to prevent this virus from spreading in the country. People should cooperate instead of questioning the government’s every move.”

On the testing confusion, Health Minister Dechen Wangmo told Kuensel that every test has its own limitation and no test is perfect. She said that the action taken in response to the Jomotshangkha incident was to align with the government’s highest prevention approach.

Dr Tshokey said that any person testing positive on the rapid test would be considered probable positive case, until proven otherwise.

Meanwhile, with the third confirmatory test coming out negative, the lockdown in Jomotshangkha is lifted from today. However, as per existing protocol of the health ministry, the primary suspect would be kept under quarantine for another seven days.

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