Covid-19: Tests on students are highly inaccurate, early findings show


30-12-20 09:50:00,

The UK government’s plans for community testing for covid-19 received a further blow this week when early results from students testing at the University of Birmingham and universities in Scotland showed that tests had a sensitivity of just 3% and that 58% of positive test results were false.

Birmingham University used the Innova SARS-CoV-2 Antigen Rapid Qualitative Test, the only officially approved lateral flow C-19 antigen test. It was sent by the government to those universities that volunteered to test students. The same test will be rolled out to test for the virus in asymptomatic students and staff in schools and universities around the country from January.1

Birmingham spent six days testing 7500 students in a process overseen by Alan McNally, director of the university’s Institute of Microbiology and Infection, who in March was seconded to set up the government’s first flagship covid-19 testing facility in Milton Keynes.

Jon Deeks, professor of biostatistics at Birmingham and leader of the Cochrane Collaboration’s covid-19 test evaluation activities, explained the results. “We found two positives in 7189 students, which scales up to 30 per 100 000 and was shocking in itself, as Birmingham has a rate of 250 cases per 100 000,” he said. “These results are especially worrying for schools: the government should not be proceeding with plans for schools testing until they have a proper evaluation of the test.”

Using polymerase chain reaction (PCR) testing, the team retested 10% of the samples that had been negative with the Innova test and found six false negative cases, raising the rate to 60 per 100 000.

Deeks said on Twitter, “We thus estimate that we found 2 cases and will have missed 60 (because we only double tested 10%). We estimate the true prevalence to be 0.86% (95% [confidence interval] 0.40% to 1.86%) which is much more credible than the 0.03% test positive rate. Our estimate of overall sensitivity is 3.2%.”

Scottish universities and colleges tested students from 30 November to 13 December, conducting a total of 43 925 lateral flow tests across all test sites.2 Of these, 79 (0.2%) were positive, although preliminary analysis of 31 of these positive samples showed that only 13 were positive on PCR testing, giving a false positive rate of 58%.

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