Question to the Department of Health and Social Care:

To ask the Secretary of State for Health and Social Care, what assessment his Department has made of the (a) rate of false positives in PCR tests in the 90 days after contracting covid-19 and (b) impact of the accuracy of PCR tests on people travelling and being required to quarantine on return.

The false positive rate of the polymerase chain reaction (PCR) test is very low at 0.005%. This does not change in the 90 days following infection as false positives are caused by external factors such as contamination during sampling and laboratory processing.

Public Health England has not made a formal assessment of the impact of the accuracy of PCR tests on people travelling and being required to quarantine on return. The day two PCR test aims to identify COVID-19 infection that has been incubating during the duration of the travel. In order to test positive at or before day two, it is likely that individuals were infected in advance of their journey. PCR therefore provides an accurate way of identifying and containing travel-associated COVID-19 cases to prevent onward transmission.