There are two different types of tests for COVID-19. The RNA or PCR test (nasal swab) determines if you currently have the virus. The second type test is the antibody test used to determine if you have been exposed to the virus. InOut Labs offers the antibody test.
What does the result of an antibody test mean?
The Coronavirus (COVID-19) Antibody Test detects the antibodies the body produces if infected by the virus. If the antibodies are in your blood it means one of two things.
- A Negative test result means that no Coronavirus (COVID-19) antibodies were detected. Follow-up testing may be necessary if indicated by risk factors.
- A Positive test result suggests that antibodies to Coronavirus (COVID-19) are present in the blood. That means the individual either IS infected or WAS infected and should follow CDC guidelines to protect him/herself as well as anyone around.
A positive antibody result does not mean you cannot catch the same virus again or a more virulent mutation of the virus (there appear to be at least three). Much like influenza vaccination (which causes your body to produce antibodies) can reduce the intensity of illness but may not prevent reinfection by the same strain of flu. There may be no protection at all against new mutations of the coronavirus.
Prior infection may (or may not) reduce the intensity and duration of illness, but not prevent infection. This is emerging science and no one really knows yet.
If you are positive for the antibodies, continue to follow the frequently changing CDC recommendations.
- The name of the virus that causes COVID-19 is SARS-CoV-2.
- Antibody tests are also known as serological tests.
IgM and IgG Antibodies:
WHEN A NEW virus invades the human body, the immune system leaps into action.
First to the scene are antibody molecules of a type called immunoglobulin M (IgM). These bind with proteins on a virus’s surface, disabling it and marking it for destruction by cells called macrophages. A few days later the system produces a second type of antibody, immunoglobulin G (IgG), to continue the ght. IgMs are short-lived. They stick around in the bloodstream for three or four weeks before disappearing. IgGs, however, are the basis for a much longer-term form of immunity. This can last for many years, or even a lifetime. (The Economist)
The RNA test conducted in hospitals is not perfect.
NY Times “False-negative test results — tests that indicate you are not infected, when you are — seem to be uncomfortably common.”
“ there is a risk of a false-negative result if the sample is not taken correctly”
[S]erological tests can also help determine if a person has been infected whether or not the individual had symptoms—something an RNA test kit cannot do after the fact, because it only looks for the virus itself. That means serological tests could be used to survey a population to determine how widespread infection rates were. It also could allow public health agencies to figure out who is already immune to COVID-19. “So if you would roll this out on a very wide scale, you could potentially identify everybody who is immune and then ask them to go back to their regular life and go back to work,” Krammer says.
This approach could be especially useful for health care providers who are working with COVID-19 patients. “They might feel much more comfortable working with those patients, [knowing] that they can’t get sick anymore, knowing that they can’t pass on the virus to others,” he says.
There are three interesting signals. A solitary positive for IgM means the person has had a very recent (potentially current) infection. Positives for both IgM and IgG mean the user was infected some time within the past month. A positive for IgG alone means that the infection occurred more than a month ago, and the user should now be immune to a repeat of it. (A negative result probably means no infection, though it could also mean that it is too early in the course of an infection for antibodies to have appeared, since the first IgMs typically turn up only 7-10 days after an infection has begun.) Scientific American
Why COVID-19 Antibody Tests Are Important
Antibody tests can indicate whether individuals have been exposed to the COVID-19 (SARS-CoV-2) virus, and whether or not they show immunity to the disease.
The implications are that a person may be able to go back to work and resume normal daily activities if they know their immune status. We already know that symptoms appear days after infection, and by the time a fever appears, they have been contagious for a number of days.
People who have recovered would have a negative PCR test (the one used to diagnose COVID-19 in hospitals) because they’ve already cleared the virus. But they would have a positive IgG antibody test indicating that they may have long-term immunity to the COVID-19.
An individual who has recovered would have circulating IgG antibodies in his/her bloodstream that provide protection from reinfection by the same virus (It is still unclear how long that immunity may last).
The CDC does not specifically discuss what to do with a positive antibody test. But a positive antibody test suggests the individual should follow these guidelines: https://www.cdc.gov/coronavirus/2019-ncov/infection-control/control-recommendations.html
The standard recommendation for anyone with a positive antibody test would be to consult with his or her physician.
Some studies on IgM and IgA antibody testing