Understanding Corona Virus (Covid-19) Antibody Testing

Numerous Corona virus antibody tests have become available to the public over the past week and as with most information regarding this virus there are lots of unknowns.  More will be known as data is gathered  and a deeper understanding of this virus and the way in which  our immune system responds continues to unfold. 

Here is a little information to understand some of the testing available and what it can and cannot tell you. 

Type of testing now available:

Nasopharyngeal (NP) or Oral Swab

  • Current test kits available under FDA approval require a nasal/throat swabbing completed by a medical professional

  • Standard of care in diagnostic settings across the country

  • Detects a current SARS-CoV-2 presence

  • Does not assess immunity with antibody presence

  • Test for the antigen (part of the virus) not antibody. 

  • Uses uses real-time polymerase chain reaction (RT-PCR) technology

  • Test supplies are heavily back-ordered on these tests, and the hospitals are being prioritized. Testing is available for other purposes on very limited quantities

Serum IgG/IgM Antibodies

  • This serology test  require a blood draw (or sometimes fingerstick)  completed in a medical care setting

  • IgM antibodies are indicative of recent exposure and are present in the early stages of infection (show up 2 to 7 days and last 6 to 12 weeks)

  • IgG antibodies usually show up within  14 days after infection (sometimes sooner)  and typically appear for months if not years after exposure. 

  • Determines whether the immune system has developed a response (antibody) to the virus

  • Varying levels of sensitivity and specificity depending on test used

 What are Antibodies and How do they Work?

Antibodies developed by the body in response to a viral infection may provide potential immunity against future infection. According to the U.S. Food and Drug Administration, COVID-19 antibody testing may indicate that “the person has been exposed to the virus and developed antibodies against it, which may mean that person has at least some immunity to the coronavirus.”

Testing may vary, for example the test used through our clinic lab is run on the Abbot platform which was approved by the FDA through their Emergency Use Authorization. It has 99.4 sensitivity but only tells you if you have had it or not  (positive or negative) but not how many antibodies you have developed. It is important to get a test that has been validated with a high specificity and sensitivity. 

As of now due to the limited understanding how this virus will behave and what type of immunity is conferred after exposure. For example: one important question is can someone who gets  a mild case get infected again?

We know people who get the flu can get it again in subsequent years.  Research is showing that the Corona virus SARS-2 seems to mutates much less frequently (10 times slower)  than influenza virus. 

We cannot tell you if you are 100% immune if you do test positive but  it is likely a positive Ab test  may convey  some level of immunity based on rapidly emerging research. CDC presumes that the risk of contracting it twice is low and hopefully they are right.  

Large numbers of people getting tested can also help researchers understand patterns within the virus and it’s transmission, allowing us to make more informed choices and to assist in the development of treatments and possibly even a vaccine or other preventative measures. 

Tests are available for cash purchase or billable to insurance.

If you’d like to learn more or get tested, call the clinic at 425-835-0359.


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Dr. Anastasia Jones