A new type of coronavirus test, often used to screen people with no symptoms, had one at the University of Birmingham, United Kingdom, in one of the few places where it was directly compared to a more accurate type of test in real life very low accuracy – world setting.
According to preliminary information from the university, only 3.2 percent of those infected with the virus received a positive result from the lateral flow tests used there among the students in Birmingham.
This is much lower than the previously stated sensitivity levels for this type of test. According to a spokesman for the UK Department of Health and Welfare, the sensitivity was 57 percent when used in a mass screening pilot in Liverpool, UK, and over 70 percent when checked in UK government laboratories.
The first type of assay being developed for the coronavirus, called the PCR test, is more accurate. PCR tests will show if the genes of the virus are present and are usually offered to people with symptoms of Covid-19. The tests usually need to be sent to a lab for processing and can take a day or two to produce results.
Lateral flow tests, also called antigen tests, are a more recent development. They indicate whether certain viral proteins are present. Similar to home pregnancy tests, they can get results in just 15 minutes.
Many organizations have started screening people without coronavirus symptoms to prevent infections from being passed on unknowingly. Because of their quick results, they often use cross flow tests. However, concerns have been expressed about their lower level of accuracy, particularly the rate of “false negative results” when someone is told that coronavirus cannot be detected when they actually incubate the virus.
The University of Birmingham was one of several UK educational institutions that offered side flow tests to all of their students before returning home for the Christmas break. Approximately 7200 accepted the offer in the first week of December and a tenth of them were randomly given a PCR test to verify the accuracy of the lateral flow tests.
The lateral flow tests showed that 0.03 percent of the students had the coronavirus. In the smaller fraction that had a PCR test, the prevalence was much higher, at 0.86 percent, according to data posted online this week.
It’s not known why the sensitivity of the lateral flow test was so low, says Jon Deeks of the university, who was involved in the screening program. One factor could be that the students took their own nasal and throat swabs and may not have done so properly, despite being supervised, and that many other sites that offer screening are also using self-swabbing.
It could also be an artifact of small numbers, says Louise Kenny of Liverpool University. The PCR positivity level resulted from 6 positive results among 710 students. “Statistically, it’s meaningless,” says Kenny.
The tests are carried out by the US-based Innova Group. A company spokesman emailed him that he was unaware of the data reported by the University of Birmingham. “The proposed low effectiveness is not known. It is therefore advisable to carefully and carefully consider the methodology used. When used correctly, the Innova test is a highly effective tool in detecting infectious individuals and enabling an appropriate response to reduce the spread of the SARS-CoV-2 virus. “
The Birmingham coronavirus prevalence from the lateral flow tests was much lower than some other UK colleges. For example, the University of Portsmouth found a prevalence of 0.2 percent among their asymptomatic students, and the University of Reading, 0.4 percent, according to a BBC report. However, according to the same report, Edge Hill University in Lancashire did not find any positive cases from around 2,100 students. It’s unclear if these other colleges asked students to wipe themselves.
Mass screening with lateral flow tests is to be introduced for all secondary school students in England from January. “There is no way they should be used like that,” says Deeks.
Allyson Pollock of Newcastle University in the UK says mass screening with lateral flow tests should not be widely implemented until it has been community tested for accuracy. “You were not assessed outside of a laboratory setting.”
A spokesman for the UK Department of Health and Welfare said via email: “The country’s leading scientists rigorously evaluated the cross-flow test and confirmed its accuracy. Our evaluation work and the running pilots help us understand how on-site lateral flow tests work and how we can use them to stop the virus from spreading. “