Covid-19 Antibody Testing (SARS-COV-2)

What antibody tests are available?

Our partner laboratories currently offer Covid-19 antibody testing. There are two antibody tests offered by the lab completed together:

• Nucleocapsid Qualitative Test

• Spike Qualitative Test

The Total Nucleocapsid antibody test can determine if an individual has had exposure to covid protein through vaccination or by acquiring the disease. The Total Spike Qualitative test does not differentiate between exposure through vaccination or through infection.

Is testing for Covid 19 antibodies currently recommended?

The current guidance is to not currently test for covid 19 antibodies. There are a number of variables that can affect whether the antibody test produces a reliable result, including the test assay used by the laboratory.

What can cause a false-negative result?

• Testing for anti-bodies less than 3 weeks after exposure or symptom onset.

• Antibody levels can wane long after an individual has had Covid-19 or vaccination against Covid-19, even if they have been vaccinated or have had Covid-19.

When should you NOT complete covid-19 antibody testing?

• You are experiencing symptoms of an active infection.

• To guide a decision to get vaccinated.

• To determine the need to quarantine after exposure to Covid-19

What are important caveats?

• There is a risk of a false-positive result with the test assay used by the laboratory (i.e. individuals with rheumatoid arthritis and heterophile antibodies AKA mononucleosis). This means the test may show you have had exposure to the virus, when in fact you have not.

• The antibody test cannot tell whether you are actively shedding the virus.

• A positive result does not mean you have protection or immunity from re-infection.

How long should I wait before getting tested if I had or suspected COVID?

A general rule of thumb is to wait 3-4 weeks after symptom onset or exposure, and 3 weeks after your last vaccine.

How do I interpret my results?

The following table provides the interpretation of the test results. If you have questions about covid-19, you can book an appointment with one of our physicians to discuss your results.

Vaccination Status	Nucleocapsid Antibody	Spike Qualitative Antibody	Interpretation
Vaccinated	+	+	Vaccinated and previously infected
Vaccinated	-	-	Vaccinated and not previously infected
Unvaccinated	+	+	Unvaccinated and previously infected
Unvaccinated	-	-	Unvaccinated and not previously infected

References

[1] https://www.publichealthontario.ca/-/media/Documents/nCoV/COVID-WWKSF/2020/07/what-we-know-serology-testing-covid.pdf?la=en&sc_lang=en&hash=C502B12A116331EAD73C4468F300459E

[2] https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests-guidelines.html