Parallel detection of SARS-CoV-2 RNA and nucleocapsid antigen in nasopharyngeal specimens from a COVID-19 patient screening cohort.

Nikolay Mayanskiy, Ekaterina Brzhozovskaya, Natalia Fedorova, Yuri Lebedin

International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases 2021 Jul

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Reverse-transcription PCR (RT-PCR) is considered the most sensitive method for the detection of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). However, this method is relatively resource- and time-consuming. This study was performed to compare SARS-CoV-2 nucleocapsid antigen (N-Ag) testing using an enzyme-linked immunosorbent assay (ELISA) with SARS-CoV-2 RNA detection. Parallel SARS-CoV-2 RT-PCR and quantitative N-Ag ELISA analysis was executed on nasopharyngeal specimens obtained during SARS-CoV-2 screening in a cohort of pre-hospitalization patients. In total, 277 specimens were examined, including 182 (65.7%) RT-PCR-positive specimens, which demonstrated a median cycle threshold (Ct) value of 27 (interquartile range (IQR) 23-35). The SARS-CoV-2 N-Ag was detected in 164 of the 182 RT-PCR-positive specimens (overall sensitivity 90.1%). Among the 95 RT-PCR-negative specimens, 72 were N-Ag-negative (specificity 75.8%). SARS-CoV-2 RT-PCR and N-Ag ELISA results demonstrated a strong agreement (Cramer's V = 0.668; P < 0.001). N-Ag concentrations spanned from 5.4 to 296 000 pg/ml (median 901 pg/ml, IQR 43-1407 pg/ml) and were inversely correlated with Ct values (Spearman's r = -0.720; P < 0.001). SARS-CoV-2 N-Ag ELISA results were in close agreement with RT-PCR results, and N-Ag concentrations were proportional to viral loads. Thus, SARS-CoV-2 quantitative antigen testing could be an additional diagnostic instrument for SARS-CoV-2. Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Citation

Nikolay Mayanskiy, Ekaterina Brzhozovskaya, Natalia Fedorova, Yuri Lebedin. Parallel detection of SARS-CoV-2 RNA and nucleocapsid antigen in nasopharyngeal specimens from a COVID-19 patient screening cohort. International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases. 2021 Jul;108:330-332