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Antibody tests. Your questions answered.

Antibody rapid tests for COVID-19 are the fast, inexpensive, and efficient tool we need to measure and monitor immunity levels.

As more of us become vaccinated against COVID-19, or recover from natural exposure, the science community is turning its attention to immunity—and how to measure it.

Antibody rapid tests for COVID-19 are the fast, inexpensive, and efficient tool we need to measure and monitor immunity levels for SARS-CoV-2. Here’s what you need to know:

What are antibodies?

Antibodies are proteins produced by the body in response to a viral infection or vaccination.

How does an antibody rapid test for COVID-19 work?

An antibody rapid test for COVID-19 is a blood test that detects if the antibodies for SARS-CoV-2 are present in the blood—either from natural infection or a vaccine. A quality rapid test will produce results in 15 minutes and test for both immediate (IgM) and long-lasting antibodies (IgG). See questions 3 and 4 for more on IgM/IgG.

Songbird’s preferred IgM/IgG antibody rapid test works like this: A blood sample (finger prick or intravenous collection) and buffer solution are added to sample well; mixed contents migrate through cassette; after 15 minutes, if a sample contains IgM, IgG antibodies or both, results will be indicated by coloured lines in the results region.

Antibody test process.

A negative antibody test result indicates none of the antibodies are present. A positive IgM result is an indication of recent infection and potential infectiousness. A positive IgG result is an indication of prior exposure or vaccination.

What is IgG and IgM?

IgM (Immunoglobulin M) are the first type of antibodies produced by the immune system in response to the virus. IgG (Immunoglobulin G) are the longer-lasting antibodies that offer protection against future disease.

IgM antibodies typically appear 7-10 days after a virus attacks and can be present during an active infection. IgG antibodies begin to appear 2-3 weeks after infection and can last for many weeks/months. IgM antibody production begins to decrease around the time IgG antibodies appear.

Do I need to test for both IgM and IgG?

Yes. Testing for both indicates what stage your immunity response is at. For example, an IgM positive indicates early stage response to a recent exposure or vaccination. An IgG positive result may indicate longer-term immunity against COVID-19. If you have the IgG antibodies, your body is more likely to recognize a future exposure to SARS-CoV-2 and then trigger your immune system to defend you from it.

How accurate are IgM/IgG antibody rapid tests?

For the most accurate results, antibody tests are deployed in the later stages after suspected exposure, infection or vaccination. Songbird’s preferred test, BTNX Rapid response COVID-19 IgM/IgG Rapid Test, has 100% IgG sensitivity 15 days after exposure and a general IgM sensitivity of 88.1%.

Songbird’s preferred IgM/IgG antibody rapid test is designed to consider antibody response from two perspectives: spike and nucleocapsid. This combined approach confirms if there is an antibody response to both vaccination and natural infections. Not all antibody tests are designed to detect both proteins and therefore may provide a negative despite the presence of antibodies from a natural exposure to SARS-CoV-2.

Who should use a rapid antibody test?

  • Anyone curious to learn if the carry the antibodies for SARS-CoV-2. (Note that testing should only occur a minimum of 14 days after exposure or vaccination.)
  • Anyone (travellers, essential workers, employees, etc.) seeking to identify prior infection or vaccination.
  • Anyone with a prior infection who is no longer symptomatic yet tests positive on a RT-qPCR test. (The high sensitivity of a PCR test can detect SARS-CoV-2 long after the infection is active.)
  • Anyone with COVID-like symptoms who tests negative on diagnostic tests for SARS-CoV-2. (A positive antibody test could indicate “long-term COVID.”

Does a positive antibody rapid test mean I am immune to SARS-CoV-2?

No. A positive result simply means you carry the IgM and/or IgG antibodies. It does not guarantee full immunity against SARS-CoV-2 or variant strains of the virus.

Does a positive IgG antibody rapid test mean I no longer need to wear a mask or follow public health measures?

No. See answer 7. Just as prior infection or vaccination does not ensure that individuals can no longer be carriers of SARS-CoV-2 or its variants, neither does a positive antibody test. Keep wearing that mask!

Why are antibody rapid tests important?

Antibody testing helps us understand the extent of SARS-CoV-2 spread in specific populations, including communities and workplaces. They also help measure overall vaccination rates and immunity levels. Regular testing at different points in time can indicate how long antibodies last to indicate risk levels for new and recurring infections. This aids future vaccine and booster scheduling.

Where can I get an antibody rapid test?

Access to quality antibody tests is limited in Canada currently. Antibody rapid tests can be purchased direct from reputable suppliers like Songbird Life Science.

Cost-effective, reliable, and fast. As we edge closer to a post-pandemic era, quality IgM/IgG rapid antibody tests are key to monitoring and managing COVID-19.