Serum SARS-COV-2 Nucleocapsid Protein: A Sensitivity and Specificity Early Diagnostic Marker for SARS-COV-2 Infection

• Published in: Frontiers in cellular and infection microbiology Vol. 10; p. 470
• Main Authors: Li, Tao, Wang, Li, Wang, Huihui, Li, Xuemei, Zhang, Shubing, Xu, Yuanhong, Wei, Wei
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 04.09.2020
• Subjects: Antibodies, Viral - blood; Betacoronavirus - isolation & purification; Biomarkers - blood; Cellular and Infection Microbiology; Clinical Laboratory Techniques - methods; colloidal gold immunochromatography; Coronavirus Infections - blood; Coronavirus Infections - diagnosis; Coronavirus Nucleocapsid Proteins; COVID-19; COVID-19 Testing; diagnostic value; Enzyme-Linked Immunosorbent Assay - methods; Female; Humans; Male; nucleocapsid protein; Nucleocapsid Proteins - blood; Pandemics; Phosphoproteins; Pneumonia, Viral - blood; Pneumonia, Viral - diagnosis; Pregnancy; SARS-CoV-2; Sensitivity and Specificity; COVID-19; colloidal gold immunochromatography; nucleocapsid protein; SARS-CoV-2; diagnostic value
• DOI: 10.3389/fcimb.2020.00470
• ISSN: 2235-2988

To explore the diagnostic value of serum severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein assay in the early stages of SARS-COV-2 infection. Serum N protein level in SARS-COV-2 infected patients and non-SARS-COV-2 infected population was measured by enzyme-linked immunosorbent assay (ELISA) double antibody sandwich assay. Colloidal gold immunochromatography assay was used to detect serum N protein antibodies in the above populations. Fifty cases of SARS-CoV-2 nucleic acid-positive and SARS-CoV-2 antibody-negative patients had a serum N protein positivity rate of 76%. Thirty-seven patients who were positive for serum SARS-CoV-2 antibody after infection had a serum SARS-CoV-2 N protein positivity rate of 2.7%. Serum N protein test results of 633 non-SARS-COV-2 infected patients, including pregnant women, patients with other respiratory infections, and individuals with increased rheumatoid factor were all negative, with serum N protein concentration <10.00 pg/mL at 100% specificity. Using SPSS 19.0 to calculate the receiver operating characteristic curve, the area under the curve was determined to be 0.9756 (95% confidence interval 0.9485-1.000, < 0.0001), and sensitivity and specificity were 92% (95% confidence interval 81.16-96.85%) and 96.84% (95% confidence interval 95.17-97.15%), respectively. The best CUT-OFF value was 1.850 pg/mL. The measurement of serum SARS-COV-2 N protein has a high diagnostic value for infected patients before the antibody appears and shortens the window period of serological diagnosis. It is recommended that the manufacturer establish two different CUT-OFF values according to the purpose of the application. One CUT-OFF value is used for the diagnosis of clinical SARS-COV-2 infection, and the other is used to screen out as many suspected cases as possible.