-by Dr. Alan Laird, Chief Medical Officer
Testing for Coronavirus has been a hot topic over the last couple of months. Below is a brief review of the types of tests available for and relating to Covid-19. There are new tests being developed all the time, so what I discuss below may not be completely up to date. Here is a brief review:
For an acute infection there is a class of tests (commonly referred to as a swab test):
- NAAT – which stands for nucleic acid amplification test. This is a group of tests that makes millions to billions of copies of part of the targeted organism (in this case the virus), so even miniscule amounts can be detected but the laboratory instrument. One type of NAAT is PCR (see below). A NAAT test for a specific bacteria or virus may take a few minutes or several hours to run depending on the type of method used.
- PCR – is the abbreviation of polymerase chain reaction. It is often what you hear about being used to solve a crime when only a small drop of blood was found and yet they could prove it was the victim’s DNA. This is currently the most common type of test for Covid-19 infection and requires special equipment for a laboratory to perform the test.
To detect a recent infection, serology testing is done (commonly referred to as a blood test). This is done by testing the blood for certain proteins that our bodies make in reaction to an infection. Those include:
- IgM – which stands for immunoglobulin M. This antibody is the first to appear in the response to an infection and may be present as soon as a few days to a week. How quickly it appears can vary from person to person.
- IgG – is the abbreviation for immunoglobulin G. This antibody arises after IgM and is detectable in the blood for a longer period of time. It is useful to show that a previous infection has occurred weeks to months earlier (and for some diseases even years earlier).
Because all of these tests can have problems, they need to be interpreted with clinical information. Meaning, was the person sick? Were they exposed to the disease? Unfortunately no test is perfect and false negatives (the test says the disease is not present when it actually is) and false positives (the test indicates the disease is present when it is not) can and do occur. The reason for those problems get very technical and beyond what can be explained in a single article.
So what testing can be done at OCAHS? While each type can be obtained here (swab or blood), we do not have the capability to perform each type, yet. Most of our swab testing is PCR and requires the swab to be sent to a reference laboratory (either Sanford in Sioux Falls or the State Hygienic lab). We have purchased the equipment to be able to complete this type of testing at OCAHS. But as you might guess, there is a high demand currently for these machines. We hope to have ours soon. Even after getting the machine here, it takes a bit to get it up and running and completely tested so it works properly before we begin using it.
IgG is available to be obtained and performed at OCAHS. If you have questions about whether you should have this test done, we encourage you to discuss it with your family healthcare provider. We hope to have IgM available in the near future. We have the equipment to perform it, but the testing supplies are in high demand and not yet readily available. We continue to explore many avenues to try to provide testing that is safe, accurate, affordable and helpful.
And as always, if you have questions about whether a test would be helpful to you or what the result means, please discuss it with your family healthcare provider. Running a test can be simple, but what that test result means for you, can be a more difficult question to answer.