The pitfalls of mass hospital health care worker testing for COVID-19.

On May 29, 2020, Ontario released an ambitious plan, “Protecting Ontarians through Enhanced Testing,” [1] for COVID-19. The approach included testing asymptomatic individuals who are at risk for infection due to suspected exposure or at-risk occupations and targeted testing campaigns for high-risk populations. Shortly thereafter, several Ontario hospitals were requested to conduct comprehensive health care worker (HCW) asymptomatic testing for COVID-19. While on the surface, broad testing of HCWs for COVID-19 seems to have merit, a deeper look raises questions regarding the rationale, effectiveness, and potential harms of this endeavour. To understand the rationale for targeting hospital HCWs for mass, asymptomatic testing, we must first ask what question we seek to answer by carrying out this testing. If the goal is to derive an estimate of community prevalence of COVID-19, hospital HCWs may or may not be representative of the general public. As a result, are we asserting that HCWs are at extremely high risk for acquiring COVID-19 despite personal protective equipment (PPE) use and are therefore driving community transmission? Studies to date have not suggested a significantly higher incidence of COVID-19 infection in acute hospital HCWs compared to the community, outside of outbreak settings [2–4]. Indiscriminate testing of asymptomatic HCWs is challenging to interpret. When asymptomatic persons test positive for COVID-19, we identify four groups with differing levels of infectious risk. In descending order, they are [1] those who are pre-symptomatic, [2] those who have a completely asymptomatic course of infection, [3] those who are recovering from infection, and [4] those with a false-positive test result. While pre-symptomatic individuals are likely as infectious as symptomatic individuals, this group will be a small minority of the true positive cases given that our current polymerase chain Dominik Mertz MD, MSc1, Gerald A Evans MD2, Susy Hota MD, MSc3 on behalf of the Ontario Infection Prevention and Control Community of Practice (see list) 1Hamilton Health Sciences Centre & McMaster University, Hamilton, Ontario; 2Kingston Health Sciences Centre & Queen’s University, Kingston, Ontario; 3University Health Network & University of Toronto, Toronto, Ontario