COVID-19 - Antibody.
Results Guide

Interpretation of COVID-19 Antibody test results

The COVID-19 Antibody Test Panel has two tests. One detects antibodies against the nucleocapsid protein of the virus particle, while the other detects antibodies against the spike protein of the virus particle.

A negative COVID-19 antibody test result means that antibodies to SARS-CoV-2 were not detected in a patient’s blood sample. This could mean that:

SARS-CoV-2 Nucleocapsid Total Antibody

SARS-CoV-2 Spike Total Antibody
  • They have not been infected with SARS-CoV-2, or
  • They have been infected with SARS-CoV-2 in the past, but their antibody levels were too low for the test to detect, or
  • They have been infected with SARS-CoV-2, but there has not been enough time for antibodies to develop (antibody response varies from person-to-person and can take up to 3-4 weeks post-onset of symptoms or post-exposure to be reliably detectable by antibody assays).
  • Some studies indicate that a small percentage of people infected with SARS-CoV-2 do not have detectible antibodies (< 4%). Immunocompromised individuals may have low antibody responses to SARS-CoV-2.
  • They have not been infected with SARS-CoV-2, or
  • They have not been vaccinated against SARS-CoV-2, or
  • They may have been infected or vaccinated against SARS-CoV-2, but the level of antibodies is too low to be detected, or
  • There has not been enough time for antibodies to develop (antibody response varies from person-to-person and can take up to 3-4 weeks post-onset of symptoms or post-exposure to be reliably detectable by antibody assays
  • Some studies indicate that a small percentage of infected people, or people vaccinated against SARS-CoV-2 do not have detectible antibodies (< 4%). Immunocompromised individuals may have low antibody responses.

A positive antibody test result means that antibodies were detected in a patient’s blood sample. This typically indicates that:

SARS-CoV-2 Nucleocapsid Total Antibody SARS-CoV-2 Spike Total Antibody
  • They have been infected by SARS-CoV-2 virus in the recent past.
  • In rare instances, falsely positive results may be caused by cross-reactivity of the test with other viruses.
  • The positive result does NOT infer immunity or protection from re-infection.
  • They have been infected by SARS-CoV-2 virus in the recent past.
  • They have been vaccinated against SARS-CoV-2.
  • In rare instances, falsely positive results may be caused by cross-reactivity of the test with other viruses.
  • The positive result does NOT infer immunity or protection from re-infection.

Interpretation of the results requires consideration of both tests together, and the most plausible interpretations are provided in the table below.

SARS-CoV-2 Nucleocapsid Total Antibody SARS-CoV-2 Spike Total Antibody Plausible Interpretation*
Negative Negative (<0.8U/ml) The results suggest undetectable levels of antibody generated in response to either natural infection or vaccination.
Negative Positive (≥0.8U/ml) The results are consistent with an immune response due to vaccination. The correlation between antibody levels and immunity is not yet established.
Positive Positive (≥0.8U/ml) The results suggest recent or prior infection with or without vaccination. The correlation between antibody levels and immunity is not yet established.
Positive Negative (<0.8U/ml) Results suggest recent or prior infection.

*Limitations of testing:

  • The COVID-19 antibody test panel is not to be used for diagnosis of an active COVID-19 infection. The molecular test/rapid antigen test may be used to diagnose active infection.
  • The result of the COVID-19 antibody test panel cannot tell you if you are infectious (actively shedding virus).
  • False negative and false positive results are possible. Patients are asked to consult with their health care providers to understand their lab test results.