More False Positives Than True Positives in the First Two Weeks of School Testing

A member of SAGE warned back in February that the return of unvaccinated children to the classroom would create a “significant risk of a resurgence” of Covid infections. This was not the case – only 0.06% of rapid Covid tests of students produced positive results in the week that schools reopened. But how many of these results were actually positive? Professor Jon Deeks, a biostatistician from the University of Birmingham, said in March: “We would expect far more false positives than true positives amongst those testing positive in schools.” New data from the Department of Health and Social Care has now confirmed that more false positive results were produced than true positives in the first two weeks of school testing.

Department of Health and Social Care

This data, as Professor Deeks points out, is a damning indictment of the use of rapid Covid testing in schools and has resulted in many children having to isolate at home unnecessarily – with their classmates often being sent home too. (At one stage, more than 200,000 schoolchildren were having to self-isolate, forcing them to miss out on much-needed catch-up work in classes.)

[The] proportion[s] false were 62% and 55% in these two weeks.

Of 2,304 positive tests, 1,353 were likely false, with one positive per 6,900 tests done.

The use of PCR tests to confirm or (in more cases) deny lateral flow test results is itself a strange choice, as Lockdown Sceptics’ Will Jones points out, and could mean that the true impact of rapid testing in schools is even worse than this data suggests.

It is interesting that they assume confirmation from a PCR test defines true and false positives, even though PCR tests are more sensitive than LFTs so are no less likely to give a positive from fragments or contamination. What if in some cases the PCR tests are just confirming the false positive of the lateral flow tests?

The British Medical Journal has been warning against the use of PCR tests for “case finding, mass screening, and disease surveillance” since last September (if not before):

PCR is not a test of infectiousness. Rather, the test detects trace amounts of viral genome sequence, which may be either live transmissible virus or irrelevant RNA fragments from previous infection. When people with symptoms or who have been recently exposed receive a positive PCR result they will probably be infectious. But a positive result in someone without symptoms or known recent exposure may be from live or dead virus, and so does not determine whether the person is infectious and able to transmit the virus to others.

Clearly, testing requirements for schools must now change. But the problem is not limited to the classroom. Professor Deeks says that false positive data should now be released for all forms of lateral flow testing.

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