Mass coronavirus testing for people without symptoms will be rolled out across England from this week. Public health officials hope that rapid and regular tests will help to identify people who have caught the virus but not fallen ill, so they can self-isolate before they spread the disease.
All 317 local authorities in England are eventually expected to offer mass testing. So far, 131 have signed up with 107 already performing tests in the community. Authorities such as Milton Keynes and Essex are focusing their tests on key workers and people who need to leave home for essential reasons. Further testing is being rolled out at major businesses.
Lateral flow tests have a strip of antibodies that bind to coronavirus. When a nasal swab is tested in the device, any virus in the sample sticks to the antibodies and shows up as a dark band or fluorescent glow on the test strip.
Lateral flow tests have pros and cons. The main advantages are that they are cheap, deliver fast results – within 30 minutes – and do not need to be processed in a laboratory. The downside is they are less accurate than the gold-standard PCR lab tests. In a trial in Liverpool, lateral flow tests missed more than half of asymptomatic cases, and 30% of symptomless people with high viral loads. This means that a person with a negative result may still be infected. Positive test results are far more reliable.
Using lateral flow tests to detect asymptomatic cases in the community is controversial and scientists are divided over the issue. Many researchers argue that even though the tests miss many cases, they can still reduce the number of people who are walking around and spreading the virus without knowing they are infected. Studies suggest one in three people with Covid-19 do not develop symptoms. The Liverpool trial found more than 3,000 asymptomatic people between November and December who were immediately told to self-isolate. How many would have developed symptoms later and been detected by routine NHS testing is unclear. Another concern is that the performance of the test drops when performed by less well-trained people.
Lawrence Young, a professor of molecular oncology at Warwick Medical School, welcomed more mass testing and said should it be targeted at those who cannot work from home. But he added that repeat testing was essential given concerns over the accuracy of the tests and that levels of virus vary over the course of the disease.
What are the pros and cons of mass Covid testing in England? The British Journal Editors and Wire Services/ The Guardian.