Diagnostic value and characteristic analysis of serum nucleocapsid antigen in COVID-19 patients.

Abstract

Background:

To date, several types of laboratory tests for coronavirus disease 2019 (COVID-19) diagnosis have been developed. However, the clinical importance of serum severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid antigen (N-Ag) remains to be fully elucidated. In this study, we sought to investigate the value of serum SARS-CoV-2 N-Ag for COVID-19 diagnosis and to analyze N-Ag characteristics in COVID-19 individuals.

Methods:

Serum samples collected from 215 COVID-19 patients and 65 non-COVID-19 individuals were used to quantitatively detect N-Ag via chemiluminescent immunoassay according to the manufacturer's instructions.

Results:

The sensitivity and specificity of the N-Ag assay were 64.75% (95% confidence interval (95% CI) [55.94-72.66%]) and 100% (95% CI [93.05-100.00%]), respectively, according to the cut-off value recommended by the manufacturer. The receiver operating characteristic (ROC) curve showed a sensitivity of 100.00% (95% CI [94.42-100.00%]) and a specificity of 71.31% (95% CI [62.73-78.59%]). The positive rates and levels of serum SARS-CoV-2 N-Ag were not related to sex, comorbidity status or disease severity of COVID-19 (all P < 0.001). Compared with RT‒PCR, there was a lower positive rate of serum N-Ag for acute COVID-19 patients (P < 0.001). The positive rate and levels of serum SARS-CoV-2 N-Ag in acute patients were significantly higher than those in convalescent patients (all P < 0.001). In addition, the positive rate of serum SARS-CoV-2 N-Ag in acute COVID-19 patients was higher than that of serum antibodies (IgM, IgG, IgA and neutralizing antibodies (Nab)) against SARS-CoV-2 (all P < 0.001). However, the positive rate of serum SARS-CoV-2 N-Ag in convalescent COVID-19 patients was significantly lower than that of antibodies (all P < 0.001).

Conclusion:

Serum N-Ag can be used as a biomarker for early COVID-19 diagnosis based on appropriate cut-off values. In addition, our study also demonstrated the relationship between serum N-Ag and clinical characteristics.

• Authors: Xihong Zhang, Chungen Qian, Li Yang, Huixia Gao, Ping Jiang, Muwei Dai, Yuling Wang, Haiyan Kang, Yi Xu, Qian Hu, Fumin Feng, Bangning Cheng, Erhei Dai
• Journal: PeerJ (PeerJ) Vol. 11 Pg. e15515 ( 2023) ISSN: 2167-8359 [Electronic] United States
• PMID: 37304882 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2023 Zhang et al.

Chemical References

• Antibodies, Neutralizing

Topics

• Humans
• COVID-19 (diagnosis)
• COVID-19 Testing
• SARS-CoV-2
• Nucleocapsid
• Antibodies, Neutralizing