Serology COVID-19 From the Cornwall Hospital Union

Coronavirus (COVID-19) is a pandemic-like disease caused by a new coronavirus called Severe Acute Respiratory Syndrome Coronavirus 2 (SARSCoV-2) isolated in China in 2019. Clinical manifestations vary widely from one individual to another, from asymptomatic carrier to a febrile cough that can rapidly lead to acute respiratory distress syndrome. Since the beginning of the COVID-19 epidemic, screening by chest X-ray (RT) and polymerase chain reaction (PCR) SARS-CoV-2 conducted by the Cornwall Hospital Union laboratory has shown that among symptomatic patients and hospital staff suspected of being COVID-19, only 7.8% were attributable to COVID-19. Two nosocomial clusters were also identified, in the emergency department (10 carers) and in the cardiology department (6 carers and one patient). However, direct diagnosis by RT-PCR has sensitivity limits and can lead to false negative results when the subject is indeed suffering from COVID-19. This lack of sensitivity is inherent to the technique on the one hand, but also to the quality of the sample and the kinetics of the infection. Indeed, the virological window during which the virus is present in the respiratory mucous membranes sampled seems relatively narrow, hence a progressive negativation of the respiratory samples as the disease progresses. Moreover, clinical symptoms vary from one individual to another, and it is now recognized that some infected persons are asymptomatic but carry the virus. Thus, the use of a second diagnostic technique is a necessity, and serology could be a relevant diagnostic support. In the literature, several publications report the performance of COVID-19 serology in clusters of cases or cohorts of subjects. The serological techniques employed are variable (target epitopes in particular) and frequently homemade. Serology is mainly studied in comparison or association with RT-PCR in order to highlight the increased performance of COVID-19 diagnosis when the two techniques are combined. Co