Ann: Cellmid Signs COVID-19 Rapid Diagnostic Supply Agreement, page-854

Sir John Bell, a Regius professor of medicine at Oxford University, who is leading the testing effort, said the assessments were ongoing and that his group was talking to companies in the hope of improving the antibody tests, adding that “a lot of the tests look very similar and probably come from the same factory in China”.

The Oxford group has characterised six different antibody tests and found that most fall well short of the accuracy required. Most failed to detect antibodies half the time and the best spotted the immune cells only 70% of the time. If used at scale, the tests could leave millions of people who have immunity convinced they are still vulnerable to the infection. For the test to pass, the accuracy would have to be nearer 95%.

https://www.theguardian.com/world/2020/apr/09/uk-government-urged-to-abandon-poor-finger-prick-antibody-tests-coronavirus#maincontent