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Published on July 28, 2020

test tube and swab for covid test

What’s the Difference Between COVID-19 Diagnostic and Antibody Tests?

The COVID-19 pandemic has given everyone a crash course in many aspects of health care. Testing is one area that leaves people confused.

There are two categories of tests for coronavirus.

  1. One is an antibody test to see if you have antibodies in your blood. This test could indicate that you had COVID in the past. The antibody test is performed on blood, and it’s the test you would want if you want to learn if you were exposed to COVID.
  2. The other is a diagnostic test to see if you actually have an active case of COVID-19 – right now. It’s done via a nasal swab. It’s the test you would get if you have symptoms and/or have been exposed to someone with COVID.

“The COVID-19 IgG antibody test is what we offer at Avera QuickLabs, and indicates if you have antibodies related to the virus,” said Nicole Sutherland, MLS (ASCP)CM, laboratory manager for outreach and support services at Avera McKennan Hospital & University Health Center. “That test may indicate that you ‘had’ the virus at some point.”

The human body’s immune system produces antibodies to fight infection. Some fight influenza, others fight off chickenpox.

“This test looks for specific antibodies to the coronavirus. If those antibodies meet a certain level, it could indicate a person has had COVID-19,” Sutherland said. “The antibody test has a high sensitivity and specificity, but each person may produce or maintain antibodies differently. That fact could influence the results of the test.”

Had It or Have It?

The other test for COVID-19 is a diagnostic test – it’s not looking at whether you “had” the virus – it may be able to tell if you have it.

“The diagnostic test is only offered with a physician’s order, and it’s not something a person can stop into Avera QuickLabs and buy for themselves,” said Sutherland. “The diagnostic and antibody tests are similar, in that they both must meet certain levels – or thresholds – to indicate a positive result. A person can be exposed to the virus but have a low viral load and the test may be negative. This is why challenges in detection and management of COVID-19 have been so tricky for people around the world, as well as here in the Midwest.”

Both tests are reliable, but hamstrung by this factor, Sutherland explained.

“You may receive IgG antibody test results that read ‘negative’ because the level of antibodies may still be developing, or your body may not have maintained them,” she said. “The other important fact is that even with a positive IgG antibody test, we still don’t know how immunity works with this virus.”

Convenience, Timing and Cost

Avera QuickLabs offers the COVID-19 IgG Antibody test for $80, and since it’s something you can voluntarily walk in and buy, it is not covered under health insurance or programs like Medicare and Medicaid.

“For people who want to know more, who wonder if they might have had COVID-19, this is a good approach, and may be less expensive than an appointment co-pay or co-insurance,” Sutherland said. “The blood is drawn and usually tested that day. It becomes part of your electronic medical record, and results also are mailed to customers, who usually get them within a couple of days.”

You can share the results with your health care provider, but the QuickLabs information only is shared with you. None of the information is used for any Avera research efforts.

“Knowledge is powerful in a time where there is a lot of confusion,” Sutherland said. “If we can help you know more about your health without an appointment, we’re happy to help you.”

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