What does the CDC Say About Diagnosing Coronavirus Using a Rapid Antibody Test?

What does the CDC Say About Diagnosing Coronavirus Using a Rapid Antibody Test?

We continue to field questions about the proper use of our OrientGene/ Healgen rapid antibody tests; it is time for an update.

At the top of the question list is: “Can I use a rapid antibody test to identify if someone is currently infected with Coronavirus?”

The opinion of the CDC is that no antibody test, rapid or otherwise, should be used to determine if someone has an active infection

While this represents the official party line about serology testing, it is interesting to look at the reasoning given by the CDC and the word selection used to express this opinion in their serology surveillance guidelines :

It can take 1–3 weeks after the first symptoms appear for antibodies to develop in the body. Since it often takes about a week for symptoms to appear after getting infected with SARS-CoV-2, antibodies could develop about 2-3 weeks after infection.

In other words, the CDC sees value in a test that can spot infection as early on as possible. 

Since antibodies take time to build up, it may be that by the time IgA, IgM or IgG antibodies have appeared, the infection will be waning.

The CDC never says the presence of antibodies cannot indicate a current infection only that the timing makes it less likely. It could be the infection and antibodies would overlap in some cases.

This is likely why they conclude the paragraph with hesitant language and state: (emphasis added by us):

“This means serology tests may not detect current SARS-CoV-2 infections and should not be used to diagnose current COVID-19.”

While it makes for some interesting discussion, because catching the virus early on is critical for getting treatment and reducing the spread, it makes good practical sense to use a PCR test or even a rapid Antigen test for early detection of Coronavirus.

Another question we field is how accurate are our rapid antibody tests?

This is usually phrased like this:

“I tested positive on the PCR test, but your rapid antibody test came back negative. Does this mean the test is not reliable?”

The answer is: “No” and there are two reasons why.

A Coronavirus test is judged based on its sensitivity and specificity.

Sensitivity asks: “How good is this test at picking up on the virus signals?”

Specificity asks: “How sure are we that the signal is from SARS-CoV-2 and not some other variation of Coronavirus (or other virus)?

PCR tests are regarded as the current gold standard for COVID-19 testing because they are exceptionally sensitive and specific which leads to fewer false negatives (sensitive) and false positives (specific).

The FDA has a lower bar for granting an EUA to a rapid antibody tests; their sensitivity needs to be 90% or higher.

This gap in sensitivity allows for more false negatives and explains why some people can test positive on one test but negative on another.

While our OrientGene/Healgen rapid antibody tests score above 95% on sensitivity, they are not perfect.

The second reason is that not everyone who contracts Coronavirus produces an antibody reaction. Even if they do, the level of antibody production may be below the detection threshold.

It also goes without saying that without being present to see how the test was performed, there is no way to know if the test was done correctly.

Which brings us to the final common question we have fielded:

“Can I hire a phlebotomist to conduct these tests? Can I hire a nursing grad student to do them for my business?”

The answer depends on how well versed this person is on reading and interpreting a rapid antibody test. In addition to knowing how to read the test, they must also know the rate of prevalence in the community where the testing is done.

Rapid antibody tests like the OrientGene/Healgen test sold by Stellar Scientific have a valuable role to play in helping determine the scope of the spread of Coronavirus.

A rapid antibody test requires more training and knowledge than you might expect.

Have questions about rapid antibody testing for Coronavirus? We are ready to help you make the best choice.