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Discrepant Results

Scientists in the UK are pushing for an investigation following reports that a number of people who tested positive for SARS-CoV-2 on lateral flow tests then tested negative by PCR, including people with COVID-19-like symptoms, according to the Guardian.

It adds that these reports appear to be concentrated in south-west England, though have also emanated from other parts of the UK.

The Guardian writes that there are a number of theories as to why there might be discrepant results and notes that no test is 100 percent perfect. One thought is that the lateral flow test could be reacting to nucleoprotein of another, seasonal coronavirus, that the PCR test does not pick up, which the Guardian says is unlikely. Another is that there is a new variant, though experts tell the Guardian that is also unlikely.

The University of Birmingham's Alan McNally tells it that an issue in the PCR testing process is a more likely culprit and calls for an audit. "If we rule out a new strain and we rule out cross-reactivity, that points to something within the PCR testing process," he tells the Guardian. "It could be anywhere from the swab being taken, to the test being done, to the result being disseminated."