Abstract
SARS-CoV-2 RNA can be detected in respiratory samples for weeks after onset of COVID-19 disease. Therefore, one of the diagnostic challenges of PCR positive cases is differentiating between acute COVID-19 disease and convalescent phase. The presence of SARS-CoV-2 nucleocapsid antigen in serum and plasma samples of COVID-19 patients has been demonstrated previously. Our study aimed to characterize the analytical specificity and sensitivity of an enzyme-linked immunosorbent assay (Salocor SARS-CoV-2 Antigen Quantitative Assay Kit© (Salofa Ltd, Salo, Finland)) for the detection of SARS-CoV-2 nucleocapsid antigen in serum, and to characterize the kinetics of antigenemia. The evaluation material included a negative serum panel of 155 samples, and 126 serum samples from patients with PCR-confirmed COVID-19. The specificity of the Salocor SARS-CoV-2 serum nucleocapsid antigen test was 98.0 %. In comparison with simultaneous positive PCR from upper respiratory tract (URT) specimens, the test sensitivity was 91.7 %. In a serum panel in which the earliest serum sample was collected two days before the collection of positive URT specimen, and the latest 48 days after (median 1 day post URT sample collection), the serum N antigen test sensitivity was 95.6 % within 14 days post onset of symptoms. The antigenemia resolved approximately two weeks after the onset of disease and diagnostic PCR. The combination of simultaneous SARS-CoV-2 antigen and antibody testing appeared to provide useful information for timing of COVID-19. Our results suggest that SARS-CoV-2 N-antigenemia may be used as a diagnostic marker in acute COVID-19.
Keywords: Antigenemia; COVID-19; Enzyme immunoassay; Nucleocapsid; SARS-CoV-2.
【저자키워드】 COVID-19, SARS-CoV-2., nucleocapsid, antigenemia, enzyme immunoassay, 【초록키워드】 SARS-CoV-2, Antibody testing, diagnostic, Antigen, COVID-19 disease, RNA, serum, sensitivity, specificity, enzyme-linked immunosorbent assay, Kinetics, PCR, nucleocapsid, antigenemia, Patient, SARS-CoV-2 RNA, enzyme immunoassay, SARS-CoV-2 antigen, respiratory, URT, information, disease, Respiratory samples, upper respiratory tract, specimens, nucleocapsid antigen, marker, Combination, COVID-19 patient, Analytical specificity, onset of disease, PCR-confirmed, serum samples, convalescent phase, enzyme, PCR positive, plasma samples, specimen, PCR-confirmed COVID-19, acute COVID-19, positive, SARS-CoV-2 nucleocapsid, positive PCR, serum sample, serum and plasma, N antigen, respiratory sample, enzyme-linked immunosorbent, was collected, median, demonstrated, onset of symptoms, resolved, 【제목키워드】 detection, Antigen, COVID-19 infection, SARS-CoV-2 nucleocapsid,