Scientists call for an urgent investigation into dozens of reports that people have tested negative for Covid PCR using the gold-standard Covid test, despite positive rapid lateral flow tests and many others experiencing Covid-like symptoms.
The UK Health Security Agency (UKHSA), stated that it was made aware of individuals in certain areas of the country reporting positive lateral flow tests results and subsequent negative PCR test results, and that they were investigating the matter.
Guardian: Scientists said they want to see more done to make sure that people infected by the virus aren't falsely assured that mixing with others is safe.
Alan McNally, professor of microbial evolutionary genetics at the University of Birmingham who helped to establish some of the Lighthouse laboratories, state-funded Covid-19 test facilities, stated: It is important that there be clear and prompt messaging from the government about which tests people should take. I would tell anyone suffering from a respiratory infection to stay home as they will likely pass it on.
If you have symptoms of a respiratory infection, and a lateral flow testing that is positive, I would assume that it's Covid-19. This message must be clear. It allows the UKHSA and the Department of Health to conduct a quality audit of the PCR testing and attempt to determine the source of the problem.
Dr Kit Yates is a senior lecturer in mathematics from the University of Bath. He said that he would recommend that the matter be investigated as soon as possible. People who test positive for lateral flow devices (LFDs), should be isolated if possible. A second positive LFD test, even if the PCR test is negative, will confirm that Covid-positive diagnosis. It is urgent that the problem be addressed.
Anecdotal evidence suggests that the problem may be more prevalent in south-west England. This leads to speculation that Sars-CoV-2 could be at the root of the problem. Scientists believe a new variant of Sars-CoV-2 is unlikely to be discovered as GPs in Oxfordshire and Manchester reported discrepancies in PCR results and lateral flow.
McNally stated that: Most PCR tests in the UK focus on three parts of the virus genome. The idea that a new variant will emerge where all three of these targets are is not going to work. This would also have been picked up by a large amount of genome surveillance.
The UK Health Security Agency stated that there was no evidence of the emergence or modification of the LFDs and that the existing variants were tested against them. They continue to perform at the expected standards.
While no Covid-19 test can be 100% accurate, there are a lot of cases that have been reported suggesting that something else is going on. These cases are not explained by math. Yates said that this is especially true in the south-west. In particular, Yates spoke of cases in which multiple LFD positives are followed by multiple PCR neutrals.
Professor Oliver Johnson, Director of the University of Bristols Institute of Statistical Science said that the percentage of LFTs passing PCR retesting (where an individual's LFT is confirmed using a PCR test), dropped in the last week test and trace report. This is a significant change considering the severity of the virus. []
Another theory is that lateral flows tests, which detect coronavirus protein nucleoprotein, mistakenly react against nucleoprotein of a seasonal coronavirus. This is possible but unlikely.
Rupert Beale is the Cell Biology of Infection Lab at the Francis Crick Institute, London. He said: Although there's a lot of potential cross-reactivity between seasonal coronaviruses and them, at least they are tested in the UK for it against three of the four seasonal Coronaviruses.
HKU1, the fourth, has not been tested as it is hard to grow this virus in a lab. It can cause common cold symptoms like shortness of breath, cough, and runny nose. Other symptoms that are similar to Covid symptoms are more common, though chest pain and fever may occur.
McNally believes that there is another explanation. If we rule off a new strain, and cross-reactivity is ruled out, then it points to something in the PCR testing process. This could include the taking of a swab, the testing being performed, and the dissemination of the results.
It would be great if someone was able to look at each lab's results and analyze the data they produce.
Susan Hopkins, chief medical advisor at the UKHSA said that if you receive a positive LFD, it is important to get a follow up PCR test to confirm that you have Covid-19. Self-isolate if you experience symptoms of Covid-19 and then take a PCR test. It is crucial to read and follow all instructions before using any test. This will help to prevent any errors.
