SARS-CoV-2 IgG Antibodies
(For past exposure)
NOTE: If you feel sick and are looking to confirm an active COVID-19 infection, please contact your local health department or healthcare provider to seek appropriate medical attention.
As the COVID-19 pandemic continues worldwide, antibody testing (also known as serology testing) is a promising new development that can play a critical role in our fight against this deadly virus. By detecting antibodies against SARS-CoV-2 in the blood, antibody testing can provide evidence that a person has been exposed to the virus and has mounted an immune response against it.
Why is this test important?
This blood test is designed to detect IgG antibodies (immunoglobulins) against the coronavirus that causes the disease called COVID-19. Over the course of an infection, the immune system produces different types of antibodies. IgG antibodies develop later in the course of an infection and may be a possible marker of immunity. The presence of IgG antibodies suggests that the infection has happened weeks to months in the past, even if no symptoms were present.
Who should consider testing?
- Individuals who have been symptom-free for at least 10 days, and who want to know if they have been exposed to COVID-19
- If you are a health care provider and believe that you may have been recently exposed to the coronavirus based on your previous signs and symptoms (such as fever, chills, cough, difficulty breathing, loss of taste/smell, muscle pain, headache, diarrhea, sore throat, fatigue, rash, etc.)
- If you have been in close contact with an individual suspected of or confirmed to have COVID-19
- If you have tested positive for COVID-19 and have recovered
- If you have had COVID-19 symptoms (such as those listed above), but did not have a confirmed diagnosis
When should someone get tested?
The timing and type of antibody test affects accuracy. If you have testing done too early in the course of infection, when the immune response is still building up in your body, the test may not detect antibodies. It is recommended that individuals wait at least three weeks since symptom onset to get this testing, and be symptom-free at the time of blood draw.
- IgG Antibodies
IgG antibodies often provide long-term protection against the specific pathogen they’re built to fight. About midway through the rise and fall of IgM production, around day 14 after symptom onset, IgG will rise above detection levels. IgG production will generally continue to rise for 28 to 35 days after symptom onset, peaking around or after clinical recovery and will remain in the blood after an infection has passed. These antibodies indicate that you may have had COVID-19 in the recent past and have developed antibodies that may protect you from future infection. It is unknown at this point how much protection antibodies might provide against reinfection.
What type of antibody testing is used?
This test is an enzyme-linked immunosorbent assay (ELISA), which is considered the laboratory standard for detecting and measuring antibodies in the blood. ELISA testing is quantitative, meaning that it determines the presence or absence of antibodies against the SARS-CoV-2 virus present in patient serum.
Is this a diagnostic test?
No. Antibody testing is not a diagnostic test to determine if you have an acute infection, but will tell you if you have developed antibodies against the virus. Until we learn more, antibody testing should not be used to change recommendations on social distancing, personal protection (face covers/masking), or work-related polices. It is vital to continue to follow COVID-19 guidelines from the Centers for Disease Control and Prevention until further notice. If you feel sick and are looking to confirm an active COVID-19 infection, please contact your local health department or healthcare provider to seek appropriate medical attention.
Do test results correlate with the severity of the disease?
No. In fact, results may indicate that you were infected with the SARS-CoV-2 virus even if you did not show any symptoms whatsoever. A person who was hospitalized in critical condition and a person who had barely a slight cough could both show antibodies to this virus.
What do positive results mean, and do positive antibodies ensure immunity?
The individual was previously infected with or exposed to COVID-19 and produced a measurable antibody response. Because this virus has only recently come into existence, scientists are still learning about the human immune response to the disease. Although the presence of antibodies against SARS-CoV-2 suggests immunity, it has not yet been proven. It is possible for immunity to be partial, or wane over extended periods of time. A positive test does not mean the individual cannot be reinfected with COVID-19 and spread it to others.
What do negative results mean?
There is no evidence the individual had a past COVID-19 infection. However, if symptoms cleared up less than two weeks prior to testing, it may be too early to detect antibodies. Negative antibody results cannot be used to rule out current or asymptomatic (showing no symptoms) COVID-19 infection. It is unclear if asymptomatically infected individuals develop any detectable antibodies. If you are immunocompromised, you may not create adequate or detectable antibodies.
How accurate is antibody testing?
Since the SARS-CoV-2 virus is structurally similar to some other viruses, there is a very small chance of a false positive test – i.e., the results can be positive even if the person has not had SARS-CoV-2 virus but has built immunity to a different virus, such as SARS-CoV-1. Also, a negative result may occur if you are tested early in your illness and your body has not had time to produce antibodies to infection.
What are the sensitivity and specificity rates for the antibody tests?
Sensitivity is the ability of a test to correctly classify a person as having antibodies to SARS-CoV-2 – thus quantifying false negatives.
Specificity is the ability of a test to correctly classify a person as not having antibodies to SARS-CoV-2.
In other words, sensitivity is the true positive rate, also considered the probability of detection. Specificity is the true negative rate, also considered the number of healthy people who are correctly marked antibody-free.
- IgG: Sensitivity-100% / Specificity-93%
This test requires blood work. You’ll receive an email within 24-48 hours with a lab requisition form and necessary instructions. Take this to a local LabCorp Patient Service Center to have your blood drawn.
All tests are authorized and reviewed by a physician from our partner laboratory.When and how will I receive my results?
Your results should be ready within 3-5 days from your blood draw. You will receive an email containing your test results along with a brief overview. You will also have an opportunity to schedule a free 15 minute consultation to review your test results.
Email a Village Green nutritionist or call 800-869-9159.
*Blood testing services are available only in the continental United States and Anchorage, AK. Not available in New York or New Jersey.
NOTE: This test has not been FDA cleared or approved. This test has been authorized by FDA under an Emergency Use Authorization (EUA).
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