What COVID-19 tests should you know about?

November 03, 2020 | by Alvaro Candel, MD
Categories: Healthy Driven Life

Are you worried that you may have COVID-19, the disease caused by the SARS-CoV-2 virus? Could you have been infected by SARS-CoV-2 and not known it? If you recovered from the virus, are you protected from getting it again?

These are questions many of us are asking. And testing can help us get answers.

We’ve heard about different tests for COVID-19, but what exactly are they used for and how do they differ?

There are currently two broad categories for COVID-19 tests: one is to check for active infection (i.e., the presence of virus) and another is to check for previous infection.

Tests to diagnose an active COVID-19 infection

If you have COVID-19 symptoms, a viral test can reveal if you are currently infected with the virus. In a viral test, a sample of fluid is collected from your respiratory system (such as swabs of the inside of the nose or throat, or saliva) to confirm the presence of the SARS-CoV-2 virus.

  • Molecular (PCR) test: A polymerase chain reaction (PCR) test is a molecular diagnostic test that detects genetic material from the virus. PCR tests are very sensitive and specific for the presence of SARS-CoV-2. There are several different types of PCR tests currently available, some of which can generate a result in as fast as 15 minutes.
  • Antigen test: An antigen test detects viral proteins found on or within the virus. Antigen tests are very specific for SARS-Cov-2, but are not as sensitive as molecular (PCR) tests. A positive antigen test, just like a positive molecular test, indicates the patient is infected with the virus and presumed to be contagious. However, since antigen tests are known to be less sensitive than molecular tests, depending on the test used and the time the specimen is collected in relation to the onset of symptoms, negative antigen test results may have to be treated as presumptive and confirmed with a molecular (PCR) test, if necessary.

For patients with a doctor’s order from an Edward-Elmhurst Health physician, COVID-19 molecular (PCR) testing is available at nine convenient outpatient lab locations. Call your doctor to talk about whether a COVID-19 test is appropriate for you. Appointments at our testing sites must be scheduled in advance.

The FDA has authorized the use of certain at-home COVID-19 test kits in which you collect your own sample (either a nasal swab or saliva) at home and mail it to a lab for processing. Home tests are available only to individuals with a physician order, and are not currently offered by Edward-Elmhurst Health.

Test to detect past COVID-19 infections

When someone is infected with a virus, their body’s immune system produces proteins, called antibodies, to help fight the infection. An antibody (or serology) test checks a sample of your blood (usually by a blood draw) for antibodies specific to SARS-CoV-2 to determine if you have been infected with this virus and have developed an immune response.

Since it can take from several days to three weeks (or longer) for the body to develop antibodies after infection, an antibody test does not tell if you are currently infected (or not) with SARS-Cov-2; a positive antibody test only tells you that you have been infected by the virus at some point in the past. It is important to remember that someone can have a positive antibody test and still be contagious to others if the infection occurred only several days prior to testing.

In addition, research is underway to determine if having antibodies can protect you from reinfection and, if so, what level of antibodies is needed for immunity and how long immunity might last. For this reason, individuals with a positive antibody test should not assume that they cannot be reinfected by SARS-CoV-2 and should continue practicing social distancing and all the other recommendations for preventing disease spread. For now, the antibody test helps experts better understand the prevalence of disease in our community.

The Centers for Disease Control and Prevention (CDC) is conducting multiple nationwide antibody studies to identify how many people have been infected by SARS-CoV-2 and to better understand the immune response to COVID-19 and whether it diminishes over time.

The antibody test can also help identify individuals who may be eligible to donate a part of their blood called convalescent plasma, which contains antibodies against the virus, and may help treat those who are seriously ill from the virus.

Edward-Elmhurst Health, in conjunction with Versiti, Inc., is looking for patients who have recovered from COVID-19 and are interested in donating plasma. The donor requirements for donating plasma are similar to those for donating blood, but also include documentation of a previous positive COVID-19 molecular (PCR) test and a clinical history of no symptoms for at least 14 days. The process for donating plasma is very similar to donating blood.  

If you are interested in donating your plasma to help treat others diagnosed with the virus, please contact Versiti directly via their website (www.versiti.org).

If you feel ill, Edward-Elmhurst Health offers screening options for COVID-19. Eleanor, your personal virtual assistant, can help you check your symptoms 24/7 and advise you on what to do next. We also offer Video Visits and E-Visits for COVID-19 symptoms.

For COVID-19 updates, please check EEHealth.org/coronavirus.

The information in this article may change at any time due to the changing landscape of this pandemic. Read the latest on COVID-19.

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