COVID-19 Testing : What you need to know.

We are now several weeks into Stay-At-Home orders in response to the COVID-19 Pandemic. As the days and weeks go by, we are learning more and more about the SARS- CoV-2 virus ( the virus causing what we refer to as COVID-19), its symptoms, treatment possibilities and testing. Lets take a look at what we know about testing.

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There are two types of testing available at this time for SARS-CoV-2 testing: 

• Diagnostic testing
• Serologic ( antibody) testing 

A diagnostic test will be able to tell a person if they have a current (or very recent) SARS-CoV-2 infection. The test methodology being used at this time is a Nucleic Acid Amplification Test (NAAT) for viral RNA (Ribonucleic acid). The test measures the presence of RNA from SARS-CoV-2 through nasopharyngeal swabs, oropharyngeal swabs, nasal swabs, sputum, saliva or bronchoalveolar lavage fluid. The sensitivity of the test varies based on both the timing of when the test was collected in relation to symptoms and the way that the sample was collected. Nasopharyngeal swab collection appears to be the most accurate for larger scale use ( just behind bronchoaleolar lavage fluid collection which involves invasive testing and cannot be used for larger scales). The Nasopharynx , which is the space between the soft palate and the back of the nose appears to have the highest concentration of virus. This is a test that is uncomfortable for the patient when collected and a collection that has insufficient specimen may produce a false negative test. Ideally, it is best to collect specimens for diagnosis early on (in the first few days when symptoms first begin) to achieve the highest sensitivity. People who are not experiencing symptoms but who actually are infected may have false negative tests. This test is best for those who are symptomatic and should ideally be performed early on. About 90% of people who develop symptoms will do so within 14 days of infection.

Antibody tests or serologic tests are used to determine which people have been exposed to the virus at some point in the past.
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These tests are performed with serum or plasma and require a blood draw. Antibody tests are not used to diagnose patients, but rather give information as to whether or not someone may have been exposed to SARS-CoV-2 in the past. Many people are questioning if the "flu-like illness" they experienced last month may have actually been SARS-CoV-2. This test gives us the ability to determine if that was indeed a possibility. Many people never develop symptoms but still may develop antibody responses. The timing of antibody development, ( IgA, IgM , IgG) varies among individuals, but it is likely best to obtain antibody tests about 14 days on average after symptoms begin. IgA and IgM rise initially followed by IgG, which is typically the antibody which confers immunity to some degree. In the case of SARS-CoV-2, we are unsure at this point if antibody testing is able to tell us if someone is immune to reinfection. It is important to keep in mind that when choosing a lab to do antibody testing , it is important to know the lab's ability to provide sensitivity and specificity data. As of the end of April 2020, there are only a handful of labs that have been granted Emergency Use Authorization by the FDA to conduct SARS-Cov-2 antibody testing.

 The understanding of SARS-CoV-2 is continually evolving as more is learned about the virus and individual's response to infection. It is important to discuss both diagnostic and antibody test options with your physician in order to obtain the safest, most accurate and appropriate testing for your needs.