Antibody tests (also known as serologic tests) can confirm whether a patient has previously experienced the coronavirus. Unlike viral tests, antibody tests require a blood sample to be taken.
Antibodies are proteins that fight off infections in the body. They usually, but not always, provide immunity against contracting that same disease a second time around. Antibodies are specific to individual diseases. Having antibodies to one specific virus will not necessarily protect against a different disease, even one that is similar.
Researchers are currently unsure whether antibodies to COVID-19 can protect people from getting re-infected with the novel coronavirus. There have been some reports of patients recovering from the coronavirus only to be reinfected a second time.
Getting an Antibody Test for Coronavirus
If an individual wishes to find out whether they have had coronavirus, they should contact their local doctor’s surgery or medical service first. The clinic will confirm the current availability of antibody testing in the area and advise the caller to where they can make an appointment.
An antibody test will look for evidence of first responder antibodies. More specifically, – IgM (immunoglobulin–M). These antibodies typically appear about 7 days after the onset of infection. The test also seeks evidence of longer-lasting IgG antibodies(immunoglobulin–G). Such antibodies are produced two to four weeks after onset.
A positive result for a COVID-19 Antibody Test
A positive test result from a coronavirus antibody test identifies that a patient may have antibodies from an infection with the virus that causes COVID-19.
If a patient receives a positive result but has no active symptoms, they are unlikely to have the infection at present. It might have already cleared up. No further follow-up is needed – unless the patient experiences severe symptoms of coronavirus at a later stage. If a person suspects that they are experiencing a second bout of COVID-19, they should seek medical advice from their local healthcare service.
As we’ve stated, it is not yet known whether having antibodies to the virus that causes COVID-19 can protect someone from getting reinfected. If they can, scientists do not yet know how long this protection might last. In this case, anyone who receives a positive result for a COVID-19 antibody test should continue to protect themselves and those around them.
If a patient tests positive on an antibody test and displays symptoms of COVID-19, they can then be referred to take a viral test. Only this test can confirm whether the individual is currently infected with COVID-19.
Limitations of Antibody Tests
The CDC advises that antibody tests are not to be used to diagnose an active case of COVID-19. If a patient wishes to find out if they are currently infected, they must seek a viral test instead.
In most cases, a person infected with a disease such as COVID-19 will develop antibodies within one to two weeks of onset. However, some people take longer to make antibodies. Others may never develop antibodies. In that case, a patient could test negative on a coronavirus antibody test despite having contracted the virus.
The CDC and their partners continue to investigate the use of antibody tests when testing for coronavirus.