Coronavirus Mutation Causing High False Negative Results In Zim-Lancet

NEW Coronavirus strains being reported worldwide could be the reason why most Laboratories in Zimbabwe have been recording high cases of false negative COVID-19 results of late, a top pathologist has said.

By Michael Gwarisa

Speaking during a virtual press briefing, Lancet Laboratories Chief Executive Officer, Dr Charlse Muronda said the viruses have changed their genetic makeup , in the process making it difficult for other  organisations which have not upgraded their testing equipment to pick the virus during testing procedures.

One of the things that have happened with COVID-19 is that over the last few months, there are new strains of the virus that have emerged. Viruses are constantly changing and we call that process Mutation. Viruses change for them to survive, if they don’t change, they will be extinct. So, with time viruses adapt and change and acquire genetic features that then makes it very difficult for the human body to detect that virus. That is why you see that every year, people get a new vaccine for flu because  flus constantly change their genetic constitution.

“This has happened in Brazil, the United Kingdom and South Africa where these mutations in the virus (SAZ COV-2) have occurred. Now these mutations pose a challenge because the number of people that are infected are high because they are highly transmissible. The virus has found a way to move from one person to the other faster and easily which means it infects more people that it would have done in the past. Also it has been discovered that these new strains have a higher virulance  in other words, their impact on the person infected is worse than the original COVID-19 virus,” said Dr Muronda.

He added that under normal circumstances and in the absence of a mutated virus, during a COVID-19 test in the laboratory, the Polymerase Chain Reaction (PCR) test extracts genetic material from the virus and then process that material to get a positive or negative result.

“But now, if the virus has changed its genetic makeup and the keys or reagents that you were using to try and detect the virus have not been adapted to be able to pick up the changes in the new virus, you will not be able to pick it up and you will call that a negative result yet it will be a false negative, the virus will be there but the system that you are using is unable to pick up that virus because the virus has mutated and changed.

“So, we have these new COVID-19 virus mutations that have come on board, obviously the things that we do at lancet is to move with technology and changes in science. Over the last three months, through our partners, we have actually managed to acquire test kits that can actually detect the viruses that have mutated.

“So if a person test positive at Lancet and then goes on to another laboratory to verify a test and they get tested and found to be negative, it does not mean the Lancet result is inaccurate, it is probably because that the other laboratory has not upgraded its equipment and therefore has failed to pick up the mutated virus and they have told this person that he/she is negative when in actual fact the person is positive. So that is actually a false negative result.”  

According to publications from the Food and Drug Administration (FDA), a lot of false negative results are largely due to the mutations in the genetic makeup of COVD-19 causing virus. Lancet has in the past few days been in public eye with clients coming forward challenging the results especially the positive ones.

“A high proportion of people infected with COVID-19 are asymptomatic and they do not have any symptoms especially young people. They don’t have the usual flu like symptoms that the typical COVID-19 patient has. They may have mild symptoms or may not feel anything at all. This person when confronted with a positive COVID-19 result will say no, something is wrong with this result.

“In the lab we also talk about the specificity and sensitivity of a test. A test which is highly specific means that you will have very few false positives. If you pick up that virus, if it is there and with the system that we have at the moment, 98% of the times the virus is picked. Nothing is 100%, there are so many instances where in a small fraction of people, you can get an erroneous result due to various reasons. The sensitivity of a PCR test is not as high as its specificity. With sensitivity, you are getting a lot of false negatives.”

He added a negative COVID-19 result does not exclude the presence of COVID-19 in the body and there were also other reasons as to why a person could get a false negative result, these include a low viral load in the body of the tested subject, taking a throat swab instead of nasopharyngeal swab, testing very early before enough viral material is present in the nasal area and inexperience on the part  of the person conducting the test.

Meanwhile, Garikai Govhati from Biomim Inc, a United States based diagnostic manufacturing company which is also working with Lancet said even though it was to early to conclude which variant and mutant virus has hit Zimbabwe, there is a high possibility that the South African mutant version could  be the one giving Zimbabwe sleepless nights

“What the FDA announced is that if you are running  a COVID-19 test and your test detects one target, you are likely to get a false negative. The Biomim test always detect two targets, one of the being the Spike protein gene where the mutations are happening.

“Currently, Biomim is one of the few testing solutions in the world that can detect these new variants and they are being recommended not only for testing but for doing the tests right before the second dose of the vaccine is administered. I wouldn’t be able to tell you which variants are being detected in Zimbabwe right now, but I would imagine they would be more South African because of the close proximity and also the travel that happens between the two the countries,” said Govhati.

As borders started to open towards the end of 2020, most countries were demanding that people that were coming into their country would have a COVID-19 certificate and this has increased demand for testing in the country. According to Lancet, they now process hundreds of tests in a single day unlike during the first wave when they would only do 20 or 30 per day.

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