Antibody Detection and Dynamic Characteristics in Patients With Coronavirus Disease 2019

Clin Infect Dis. 2020 Nov 5;71(8):1930-1934. doi: 10.1093/cid/ciaa461.


Background: The coronavirus disease 2019 (COVID-19), caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been rapidly spreading nationwide and abroad. A serologic test to identify antibody dynamics and response to SARS-CoV-2 was developed.

Methods: The antibodies against SARS-CoV-2 were detected by an enzyme-linked immunosorbent assay based on the recombinant nucleocapsid protein of SARS-CoV-2 in patients with confirmed or suspected COVID-19 at 3-40 days after symptom onset. The gold standard for COVID-19 diagnosis was nucleic acid testing for SARS-CoV-2 by real-time reverse-transcription polymerase chain reaction (rRT-PCR). The serodiagnostic power of the specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against SARS-CoV-2 was investigated in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and consistency rate.

Results: The seroconversion of specific IgM and IgG antibodies were observed as early as the fourth day after symptom onset. In the patients with confirmed COVID-19, sensitivity, specificity, PPV, NPV, and consistency rate of IgM were 77.3% (51/66), 100%, 100%, 80.0%, and 88.1%, respectively, and those of IgG were 83.3% (55/66), 95.0%, 94.8%, 83.8%, and 88.9%. In patients with suspected COVID-19, sensitivity, specificity, PPV, NPV, and consistency rate of IgM were 87.5% (21/24), 100%, 100%, 95.2%, and 96.4%, respectively, and those of IgG were 70.8% (17/24), 96.6%, 85.0%, 89.1%, and 88.1%. Both antibodies performed well in serodiagnosis for COVID-19 and rely on great specificity.

Conclusions: The antibodies against SARS-CoV-2 can be detected in the middle and later stages of the illness. Antibody detection may play an important role in the diagnosis of COVID-19 as a complementary approach to viral nucleic acid assays.

Keywords: COVID-19; ELISA; SARS-CoV-2; diagnosis; serological test.

MeSH terms

  • Adult
  • Aged
  • Betacoronavirus / immunology
  • COVID-19
  • COVID-19 Testing
  • Case-Control Studies
  • Clinical Laboratory Techniques / methods*
  • Coronavirus Infections / blood
  • Coronavirus Infections / diagnosis*
  • Enzyme-Linked Immunosorbent Assay / methods*
  • Female
  • Humans
  • Immunoglobulin G / blood*
  • Immunoglobulin G / immunology
  • Immunoglobulin M / blood*
  • Immunoglobulin M / immunology
  • Male
  • Middle Aged
  • Pandemics
  • Pneumonia, Viral / blood
  • Pneumonia, Viral / diagnosis*
  • Reverse Transcriptase Polymerase Chain Reaction
  • SARS-CoV-2
  • Sensitivity and Specificity
  • Time Factors


  • Immunoglobulin G
  • Immunoglobulin M