Q & A: Antibody Testing

Your Questions Answered

COVID-19 Antibody Testing

 

 

Q: What is SARS-CoV-2?

A: SARS-CoV-2 stands for Severe Acute Respiratory Syndrome Coronavirus Type 2, which is the name of the virus causing the current COVID-19 pandemic.

 

Q: What tests are being offered for COVID-19?  

A: There are two types of tests available for COVID-19 that can detect whether a person had it in the past or if a person currently has it in the present.

    1. Detecting past infection – the antibody test uses serology testing, which tests for antibodies against SARS-CoV-2, the virus that causes COVID-19.
    2. Detecting current infection – the polymerase chain reaction (PCR) is a molecular diagnostic test that tests for active infection.

 

Q: What are the differences between the tests?

A:  The antibody test detects if a patient has had evidence of a previous COVID-19 infection. The test is done via blood draw and detects the body’s antibody response to the infection.

 

Antibodies develop when the immune system responds to a germ, usually a virus or a bacterium. With other diseases, IgG is one type of antibody that usually develops 3 to 4 weeks after infection with the germ and lasts for a long time. Once you have IgG antibodies, your immune system may recognize the germ and be able to fight it the next time you are exposed to it. Infection with the virus does seem to result in the production of IgG antibodies, though it isn’t known exactly when that happens and if it happens to everybody.

 

The PCR test that is a nasal swab molecular test detects the actual COVID-19 virus, and an indication of active infection.  These tests detect the virus’s genetic code (RNA and DNA) and amplifies it so it can be detected.  Detection of that DNA leads to a positive test.

 

Q: Who is a good candidate for the antibody test?

A:   A typical candidate for the antibody test has no current symptoms, but they may have had some symptoms in the past or suspect they had prior infection.

 

Q:  Who is a good candidate for the molecular test?

A: A typical candidate for the molecular test is someone who has active symptoms for COVID-19.  Per the CDC, people with COVID-19 have had a wide range of symptoms reported – ranging from mild symptoms to severe illness. Symptoms may appear 2-14 days after exposure to the virus. People with these symptoms or combinations of symptoms may have COVID-19: cough and shortness of breath or difficulty breathing or at least two of these symptoms: fever, chills, repeated shaking with chills, muscle pain, headache, sore throat, and/or loss of taste or smell.

 

Q: What is the process for getting the tests?

A: During a medical evaluation a clinician will determine which test is best for you. Dependent on your current and past symptoms, the clinician will choose from three options.

 

1. Antibody test – for patients that are not actively sick that may have shown previous symptoms such as a past cold or flu like symptoms this test will see if your body reacts to the virus thus indicated previous infection. This test uses a sample of blood taken during your patient visit.

 

2. Molecular diagnostic test – for patients that are currently showing COVID-19 symptoms this test will determine if you are currently infected. In most cases, a nose or throat swab is taken by a healthcare provider, and that swab is sent to the lab for testing.

 

3. No test – in some instances after discussion with a clinician, because of the possibility of false positives or negatives, no test may be most appropriate.

 

Q: How long do the antibody test results take? 

A: The results of the antibody test will be available within 48 hours, some patients have received results in as few as 24 hours. The results of the tests will be shared with you either via your own personal lab account website or by phone call from one of our representatives.

 

Q: What test results for the antibody test will be reported?

A: The results for the antibody test are reported as reactive, nonreactive, or indeterminate.

  • Reactive: A reactive result indicates that IgG antibodies to the virus were present in your blood specimen. A reactive result can mean you had infection with the virus in the past or it can mean you are currently infected. If you did not test positive for coronavirus already, another test may be needed to see if you are currently infected.
  • Nonreactive: A nonreactive result means that IgG antibodies to the virus were not present in the blood. However, you may still be infected which can be detected by the molecular test.
  • Indeterminate: An indeterminate result means that the test did not produce a clear nonreactive or reactive result. This could happen if the test reacted with other antibodies in the blood or if you do have the coronavirus antibodies but the levels are still too low to be reported as reactive.

 

Q: What test results for the molecular test will be reported?

A: The results for the molecular test is positive or negative.  A positive test states the virus was detected from your sample.  A negative test states no identifiable virus was found.  Correlation with your symptoms helps improve the utility of the test and how it is used.

 

Q:  I tested reactive (positive) for the antibody test, what should I do?

A: A positive antibody test means that you have been infected with COVID-19 in the past and that your immune system developed antibodies to try to fight it off. It can identify people who had an infection in the past, even if they had no symptoms of the illness. It is helpful to know if you are positive as it may be able to help determine some level of immunity to COVID-19. This could be one tool in the decision of who could safely work in certain jobs. In some cases, it could help determine when the COVID-19 illness occurred. It can also help determine who qualifies to donate convalescent plasma (a blood product that contains antibodies against COVID-19 and can be used as a COVID-19 treatment). If lots of people take the test in a community, it can help public health leaders and researchers know what percentage of the population has already had COVID-19.

 

Q:  If I test positive to the antibody test am I immune to COVID-19?

A: The antibody test detects if you have had a prior infection of COVID-19.  Because this virus is so new and we are still learning about it, if you do develop antibodies we cannot say with certainty that this equates to immunity and/or the duration of the immunity. Even with antibodies you should still practice social distancing and wearing masks in public.

 

Q: What is the cost of the test?

A: Patients should check with their insurers to see if the tests are covered under your insurance plan. If you do not have insurance the general cost of the antibody test and PCR ranges between $50-100.

 

Sources
Dr. Joe Chow, President – TeamHealth Ambulatory Care
Dr. Shyamal Majithia, Medical Director WNY Immediate Care
Texas Department of Health State and Health Resources COVID-19 Testing: PCR Versus Serology Testing, Explained Version 1.0. Released 4/20/2020.