Saliva tests for Covid-19, which are being introduced for NHS workers as part of the government’s mass testing programme, pick up only 13% of people with low levels of the virus and not 91%, as the official assessment has claimed, according to experts.
Two members of the Royal Statistical Society’s working group looking at the accuracy of Covid tests have questioned the results and the way they have been evaluated.
Prof Jon Deeks from Birmingham University and Prof Sheila Bird, formerly of the MRC Biostatistics Unit at Cambridge University, say the tests perform poorly where people have low levels of the virus, which is often the case in people without symptoms.
They say the discrepancy in the figures is because the evaluation used “spiked” samples – saliva to which the virus has been added in the lab. Those manufactured samples were picked up efficiently by the test, but “real world” samples from people with asymptomatic Covid were not.
— to www.theguardian.com