Oxford University researchers found that antibody tests to more than 900 healthcare workers to detect whether a person is COVID-19 positive or not might be missing those who only experienced mild Coronavirus symptoms.
The researchers noticed that among the results a significant number of reports showed negative, including those people who were most likely to have contracted the disease, which killed over 46,000 only in the U.K. This discovery has raised concerns and doubts over the accuracy of such Coronavirus tests. The researchers are now worried about the use of these tests which are supposed to help the country to avoid another lockdown may not be correct.
The Inaccurate Test
As per the study, researchers found that a third of those who tested negative for antibodies claimed that they had previously lost their sense of smell or taste—which are the common symptoms of Coronavirus infection. Among those who took the test, 387 people came just below the threshold needed for a positive COVID-19 result, but never complained about developing any symptoms.
Dr. Tim Walker, who is one of the researchers involved in this study, told the Telegraph that the suggested threshold for what counts as a positive result has been set too high. He added that 'You can see that below the cut-off, there is a rising proportion of people who report a loss of their sense of smell or taste," and this has indicated that the test threshold is missing people with mild Coronavirus infection. "Of course there will be plenty of people, too, who will have had no symptoms whatsoever and will still have antibodies," he said.
Antibody tests can reveal whether a person was previously infected or not through the signs in blood that can only happen if a person has been exposed to the virus. The test should be able to tell whether someone has had Coronavirus infection at any time in their life, which other tests cannot reveal.
Previously it was reported that the government of the U.K. has decided to distribute millions of antibody tests for free to the residents. These tests have been on sale privately over the last few months. Currently, in the country there are four types of tests that are being used and all of them were given to the Oxford study volunteers. But the new study results suggested that the tests may be on average up to 11 percent less accurate than it is believed.
Researchers have urged for a reassessment of the threshold between negative and positive results, as there is still very little clarity about how effective antibodies are in terms of protecting people from catching novel Coronavirus a second time, or how long this immunity might last.