key: cord-0772217-ur6j7v97 authors: Ahava, M. J.; Kurkela, S.; Kuivanen, S.; Lappalainen, M.; Jarva, H.; Jaaskelainen, A. J. title: Detection of SARS-CoV-2 nucleocapsid antigen from serum can aid in timing of COVID-19 infection date: 2021-01-13 journal: nan DOI: 10.1101/2021.01.08.20248771 sha: 165dce7fa029ce163174afa00f044cf95981e893 doc_id: 772217 cord_uid: ur6j7v97 SARS-CoV-2 RNA can be detected in respiratory samples for weeks or even months 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. Recently, the presence of SARS-CoV-2 nucleocapsid antigen in serum samples of COVID-19 patients was published [Le Hingrat et al. Detection of SARS-CoV-2 N-antigen in blood during acute COVID-19 provides a sensitive new marker and new testing alternatives, Clinical Microbiology and Infection, 2020]. 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 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 a PCR-confirmed COVID-19. The specificity of the Salocor SARS-CoV-2 serum N 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 94% 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. The combination of simultaneous SARS-CoV-2 antigen and antibody testing appeared to 34 provide useful information for the timing of COVID-19. Our results suggest that SARS-CoV-35 2 N-antigenemia may be used as a diagnostic marker in acute COVID-19. All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. on the performance of serum antigen tests as a diagnostic method for SARS-CoV-2. The aim of this study was to characterize the analytical specificity and sensitivity of an perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The here-evaluated Salocor N-antigen ELISA (Salofa) is based on a double antibody 91 sandwich ELISA test. The assay protocol is described in the Supplement. The 95% Clopper-Pearson confidence intervals were calculated for sensitivity and specificity perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. ; https://doi.org/10.1101/2021.01.08.20248771 doi: medRxiv preprint 6 Using COVID-19 panel A, we calculated test sensitivity in relation to disease onset (Table 1) . 106 The sensitivity with specimens retrieved at ≤14 days post onset was 94%, and decreased to 107 50% with specimens retrieved 15-21 days post onset ( Table 1) perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. ; https://doi.org/10.1101/2021.01.08.20248771 doi: medRxiv preprint perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. ; https://doi.org/10.1101/2021.01.08.20248771 doi: medRxiv preprint perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. 235 All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. ; https://doi.org/10.1101/2021.01.08.20248771 doi: medRxiv preprint perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted January 13, 2021. ; https://doi.org/10.1101/2021.01.08.20248771 doi: medRxiv preprint Detection of 2019 novel coronavirus (2019-nCoV) 171 by real-time RT-PCR Molecular and Serological Tests for COVID-19 a Comparative 173 Review of SARS-CoV-2 Coronavirus Laboratory and Point-of-Care Diagnostics Laboratory Testing Methods for Novel Severe 179 Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) Detection of SARS-CoV-2 N-antigen in 182 blood during acute COVID-19 provides a sensitive new marker and new testing 183 alternatives Serum SARS-CoV-2 185 nucleocapsid antigen detection is essential for primary diagnostics of SARS-CoV-2 186 associated pneumonia Performance of six SARS-CoV-2 188 immunoassays in comparison with microneutralisation Comparison of two commercial 191 platforms and a laboratory developed test for detection of SARS-CoV-2 RNA. medRxiv Prolonged presence of viral nucleic acid in clinically 194 recovered COVID-19 patients was not associated with effective infectiousness. Emerg 195 Microbes Infect Prolonged SARS-CoV-2 detection and reversed RT-PCR 197 results in mild or asymptomatic patients Nucleocapsid Protein as Early Diagnostic Marker for 200 SARS Novel system for detecting SARS coronavirus 202 nucleocapsid protein using an ssDNA aptamer preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted