Prof J Bell Article 5th April15 May 2020 11:17
Interestingly the good professor wrote this article just before the RTC was formed over a month ago. I've copied the link and posted some particularly relevant excerpts from it below:
https://www.research.ox.ac.uk/Article/2020-05-13-covid-19-drugs-trial-rolled-out-across-uk-homes-and-communities
"To validate these tests you need to obtain a range of tools. You need a gold standard test so you know the correct answer and you need sera from patients who have recovered from the virus infection they had approximately 28 days before. You also need blood from people who donated before the epidemic so you know whether you falsely see positive tests when there is no Covid-19 in the sample. For example, there are a number of other coronaviruses circulating that might stimulate antibodies that cross react to Covid-19 proteins. It has taken some time to gather these tools for validation but the UK is now uniquely positioned to evaluate and find the optimal test for this disease. We clearly want to avoid telling people they are immune when they are not, and we want all people who are immune to know accurately so they can get back to work.
Multiple tests have been provided for evaluation, and a range of convalescent sera has been used to determine whether the tests can identify both low and high levels of antibodies. We have been very careful to test using gold standards checked against a sensitive enzyme-linked immunosorbent assay (Elisa) of the spike protein and other viral proteins. Sadly, the tests we have looked at to date have not performed well. We see many false negatives (tests where no antibody is detected despite the fact we know it is there) and we also see false positives. None of the tests we have validated would meet the criteria for a good test as agreed with the MHRA. This is not a good result for test suppliers or for us.
Interestingly we are not the only ones who having difficulty identifying commercial tests that work in a home test kit format. The Spanish apparently returned test kits that were not working, and the Germans who are developing their own sensitive kits believe they are three months away from getting these available and validated. Not test has been acclaimed by health authorities as having the necessary characteristics for screening people accurately for protective immunity.
What next? We will of course continue to look for a test that meets the criteria of an acceptable test. There is a point in evaluating these first-generation tests where we need to stop and consider our options. We effectively need an Elisa on a membrane, with the same sensitivity and specificity that can be used at home. That should be achievable, and the government will be working with suppliers both new and old to try and deliver this result so we can scale up antibody testing for the British public. This will take at least a month."
Professor Sir John Bell, GBE, FRS
Regis Professor of Medicine Oxford University