As we begin to look to the other side of the peak of COVID-19, this issue of more widespread testing of patients, staff (and indeed the general population) for infection with the SARS-CoV-2 virus whether or not they have symptoms is looming large. We need to think carefully about the risk of false positives when interpreting the meaning of a positive PCR test in a group of people with a low prevalence of SARS-CoV-2. To this point in the UK, most testing has been focused on those with symptoms (patients admitted to hospitals, community cluster investigation, staff off work with symptoms). However, these a lot of discussion currently about how far to extend testing to include patients, staff, and members of the general public who have no COVID-19 symptoms. There’s a lot of logic to doing this – there’s undoubtedly a pool of asymptomatic and pre-symptomatic SARS-CoV-2 infected individuals who are contributing to transmission.