This TRC Hot Topic webcast features an expert panel discussion and clinical guidance for COVID-19 antibody testing. Listen as Michael E. Klepser, PharmD, FCCP, FIDP and other panelists discuss and answer common clinical questions, including:
- What does an antibody test detect?
- When do you recommend antibody testing?
- What are the limitations of antibody testing?
- How common are false positives with antibody tests?
Here’s an excerpt of the
COVID-19 Antibody Testing webcast:
Lori Dickerson: We’re writing about this now because of course we’re all getting questions about antibody testing for SARS-CoV-2, now that point-of-care fingerstick tests are entering the scene.
Mike, to get us started, to set the stage, can you give a general overview of how antibody tests differ from diagnostic tests for SARS-CoV-2, for example, such as what they detect and how they’re collected?
Michael Klepser: Sure. The diagnostic tests that are out there currently tend to use PCR to detect RNA fragments and then amplify those, or antigen tests, which, again, is a physical component of the virus itself.
The antibody tests are looking to measure the presence of antibodies that are generated to typically give a nucleocapsid or the spike protein from the SARS-CoV-2 virus. So they differ in that you’re not detecting something that’s actually present in the body that’s being produced by the virus. But you’re looking at the body’s response to one of the elements from the virus.
Currently the PCR tests, or the diagnostic tests, are collected usually looking at respiratory specimens: nasal swabs or saliva testing; whereas the antibody tests are typically evaluating some component of the blood.
Lori Dickerson: Great setup, Mike. I appreciate that. We started out by mentioning this new point-of-care test that’s available, the Assure/FaStep test. Can you give a little background on this new test and how it works, and also if you think having this point-of-care test will change the landscape for antibody testing?
Michael Klepser: It’s important to take it back one step and remember that currently antibody tests are not widely recommended either by the WHO or by the CDC. Really there’s still a lot of questions regarding what does an antibody mean, or what does the results of an antibody test mean.
With that, looking at this new test, it’s interesting because it is one of the first that is usable at a point of care. It’s received its Emergency Use Authorization for a fingerstick specimen, and it’s CLIA-waivable. So it can be done in a non-traditional-laboratory setting, specifically someplace like a physician’s office, perhaps an emergency department or an urgent care, that is not going to be running the specimens down to the central lab, or even a pharmacy that possesses a certificate of waiver.
This test itself essentially provides a yes/no result. Do you have antibodies, yes or no? Do you have the immediate-phase antibodies (the IgM), or the more longer-term antibodies (the IgG)? It doesn’t give you the amount of antibodies, it doesn’t give you a ratio of an antibody; it just is a yes/no result.
Lori Dickerson: Mike, a point of clarification there, because we do say this in our article: “It gives a qualitative yes or no result in about 15 minutes,” but we have a question coming in: Is that just the case for this Assure test, that’s it’s qualitative, and the other non-CLIA-waive laboratory-based antibody tests are quantitative, or are they also qualitative?
Michael Klepser: Not all of them. It depends on the test. You know, as confusing as the diagnostic tests are, the antibody tests are even more confusing, because some of them just report out total antibodies; some of them differentiate between IgG/IgM, some of them are qualitative, some of them are quantitative. So you really need to know what test you’re using before you start to apply it to your clinical practice.
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