INFORMATION ABOUT COVID-19 ANTIBODY BLOOD TEST FOR THE PUBLIC
There has been a lot of information in the news lately about Covid-19 antibody testing. As such, we hope the following information helps you understand more about testing.
1. Why would anyone want to test for COVID-19* antibodies?
The theory goes like this… If you have antibodies against COVID-19 that might indicate that you’ve had the infection and hopefully that you are now immune from re-infection.
The problem is, however, the current tests do not prove you are immune to this disease or even prove that you are no longer infected by the virus and whether you are still contagious to others.
2. What is an antibody?
An antibody is a large protein produced by our immune system in order to recognize and remove potentially harmful foreign substances such as viruses and bacteria.
3. Does COVID-19 antibody testing measure antibodies against that virus and can it prove that I am immune?
-We actually make a few different antibodies against various parts of the virus.
-We do not yet know which, if any, of these different antibodies help kill the virus.
-We know from other diseases that not all of the antibodies help kill the virus.
-Each test is designed to find just one very specific antibody against COVID-19.
In addition, they are not yet measuring the actual amount of antibodies we make.
We know from other viruses you need to make a certain amount to become immune.
The current tests cannot claim that the antibody they identify will help kill the virus or that you are making enough of the right antibody to be immune from future infection.
4. Does a negative antibody test (no antibodies found) prove you have never been infected with COVID-19?
No. Antibody testing should not be used to diagnose or rule out COVID-19 infections. Infections should be diagnosed with the nasal swab PCR test, looking for the viral RNA.
It can take two weeks or more to start making the IgG antibodies they are testing for.
So if you test a person too early, the test indicates they are not infected when they are.
It is very dangerous to have a COVID-19 infected person believing that they are OK when they actually have an ongoing, very dangerous and contagious disease.
5. Does a positive antibody test (antibodies found) prove you have been infected?
No. Again, antibody blood tests should not be used to diagnose a COVID-19 infection.
A positive test could mean you are infected now or you were infected in the past.
There can be false positive results meaning they found a different viral antibody and mis-read it as a COVID-19 antibody. This is most likely to happen with one of the six other Corona viruses known to infect humans.
-We do not know if they are looking for the right antibody…
-We do not know if you are making enough antibodies…
-We do not know if you are currently infected, or were in the past or perhaps never…
-We do not yet know how long any such immunity might last, weeks, months or years??
-All of this makes the current COVID-19 antibody test results very tricky to interpret.
6. Sounds like we’re not yet ready to do antibody testing for COVID-19?
These tests may be very helpful for Public Health Department investigations, for use in scientific studies and in a few particular clinical situations.
But they are not appropriate for making a COVID-19 diagnosis and at this point they are not adequate to prove that a person is not infectious or immune to the disease.
CDC scientists and others are working diligently to better understand the level of antibodies needed for protection, the duration of that protection, and the factors associated with whether a person develops a protective antibody response.
* COVID-19 is the name of the disease caused by the SARS-CoV-2 virus. For simplicity we have chosen to use COVID-19 to refer to both the disease and the virus.
UPDATED COVID-19 TESTING INDICATIONS
If you have a cough and fever caused by a COVID-19 infection and you are only mildly ill the current treatment plan includes:
- Stay home/avoid close contact with others, especially vulnerable people, such as the elderly.
- Self quarantine until you have no fever, without fever reducing drugs AND your symptoms are improving for 3 days; AND at least 7 days from the start of your illness.
- The usual viral illness treatment: good hydration, nutrition and acetaminophen for pain/fever.
- Seek medical advice if, for example, you are short of breath, light headed or getting worse.
- Ideally, you should call your own doctor for the most appropriate evaluation plan.
- Call a local Urgent Care for advice if you have no doctor available.
- Go to a local hospital ER if you think you are sick enough to need hospitalization.
If you have a mild cough and fever NOT caused by a COVID-19 infection but rather by some other viral respiratory illness, we are currently recommending the exact same treatment plan.
One reason for this common treatment plan is that the current estimates for the “false negative” COVID-19 test result rate is over 20%. So even if you have a negative test, it does not adequately “prove” that you do not have the COVID-19 infection.
COVID-19 testing will not change the treatment plan for the majority of patients with mild cough, fever and other respiratory infection symptoms.
Most COVID-19 infected patients who seek medical care have had fever, cough, fatigue and no appetite. Almost half have reported shortness of breath, aches and pains, and sputum production. Other symptoms experienced by a small but significant number of COVID-19 patients are, headaches, sore throat, congestion, diarrhea, nausea and a decreased sense of smell and taste.
This constellation of symptoms is not currently unique enough to reliably differentiate COVID-19 infections from a number of other viral respiratory infections, such as influenza A and B.
Mildly ill patients generally need no acute medical care or testing unless they are in a high-risk group or live and work around medically vulnerable people. For example, Healthcare Workers.
Moderately ill patients should be tested for COVID-19, especially if they are in a high-risk group or live and work around medically vulnerable people.
Seriously ill patients need to be more fully evaluated, in an appropriate health care setting, for potential hospitalization and further testing.
We are expecting another potential indication for COVID-19 testing as we approach what may be a challenging allergy season this spring. Congestion, sneezing, fatigue and even some shortness of breath with a mild cough can be associated with seasonal allergies in some patients. Therefore, in some people allergy symptoms may present in a way that is also consistent with COVID-19 infection.
Differentiating between allergic upper airway symptoms and COVID-19 infection may become very important to various people depending on our local home isolation policies, their work place encounters and social interactions. People cannot spread “allergies”, but they can spread disease.
You can learn more about the COVID-19 Test Guidelines here:
For more general information about COVID-19:
Homemade Masks and COVID 19 - more information