SARS-CoV-2 nucleocapsid antigen in urine of hospitalized patients with Covid-19

Abstract

Introduction: SARS-CoV-2 nucleocapsid antigen (N-Ag) can be detected in the blood of patients with Covid-19. In this study, we used a highly sensitive and specific nucleocapsid-Ag assay to explore the presence of N-Ag in urine during the course of Covid-19, and explore its relationship with the severity of the disease. Material and Methods: Urine and blood samples were collected from 82 patients with a SARS-CoV-2 infection proven by PCR and included in the COVIDotheque. We explored the presence of N-Ag in urine and blood using the AAZ N-Ag test, studied the kinetics of the marker according to the time since the onset of symptoms and evaluated the association between N-Ag levels, clinical severity and inflammation. Results: In the first and second weeks of Covid-19, hospitalized patients tested positive for urinary N-Ag (81.25% and 71.79%, respectively) and blood N-Ag (93.75% and 94.87%, respectively). N-Ag levels in urine and blood were moderately correlated with the number of days after the onset of symptoms (r=-0.43, p<0.0001; r=-0.55 p<0.0001, respectively). The follow up of seven SARS-CoV-2 infected patients confirmed the waning of N-Ag in urine and blood over the course of the disease. High urinary N-Ag levels were associated with the absence of SARS-CoV-2 nucleocapsid-IgG (N-IgG), admission in intensive care units, high C-reactive protein levels, lymphopenia, eosinopenia, and high lactate dehydrogenase (LDH). Conclusion: Our study demonstrate that N-Ag is present in the urine of patients hospitalized in the early phase of Covid-19. As a direct marker of SARS-CoV-2, urinary N-Ag reflects the dissemination of viral compounds in the body. Urine N-Ag is a promising marker to predict adverse evolution of SARS-CoV-2 infections.