Frank Bures: Differences in COVID testing | Lifestyles
If someone has just come out of a cave after 3 years of hibernation, he or she would be appalled at how much COVID viruses are consuming us as we consume cascades of virus information. One of the current topics is testing for the viral presence of COVID one way or another. Not all tests are created equal. This will be a brief tutorial on the differences.
There are two broad categories of COVID tests. The former are those that find the active viral presence, and the latter are the tests that find their fingerprints in the form of antibodies after making their escapade, which are for another clue. The two varieties that attempt to track down viral vermin in their moist mucous hiding places are known as molecular testing (PCR) and also known as nucleic acid amplification testing (NAAT) and rapid antigen testing. or protein capsule or RATS.
The basic structure of a virus is made up of the genetic material, which is either DNA or RNA, deoxyribonucleic acid or ribonucleic acid. SARS-C0V-2 is an RNA race. Discussing the differences is really complicated. Surrounding the RNA is an envelope, capsule or nucleocapsid of protein. Surrounding this, on some viruses, is a fatty or lipid envelope or coating, which is the case here, containing the spike and membrane proteins.
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The two types of tests to find viral traces both start with a nasal swab. It used to be the 4ft long one that lit your nose all the way to the back of your throat or nasopharyngeal area (doing a brain biopsy at the same time?). But the CDC decided some time ago that the short swab used just inside your nostril was sufficient. A saliva sputum was also used. The data does not specify which method collects the best sample with the most virus. The sample is treated with simple chemicals that separate the viruses into their component parts.
The technique of PCR or molecular assay is really complicated to discuss. It is an ingenious method of multiplying viral amino acids hundreds to thousands of times via PCR or polymerase chain reaction to detect even the smallest amount of virus. It does not determine if it is alive and able to infect or not, just if it is there on the snot or sampled surface.
An antigen test uses antibodies made in a laboratory against a substance that causes your body to produce an immune response. This end point is the generation of antibodies directed against this antigen. Most antigen tests use technology called lateral flow testing, which dates back to the 1940s. One of the most common uses now is over-the-counter home pregnancy tests. The preparation is a special paper, which contains laboratory antibodies against the proteins of the COVID capsule, where the letter T (for test) is on the plastic cassette. The C (control) line on the cassette contains laboratory antibodies to common throat or nose germs, such as proteins from the bacteria Streptococcus C. The appearance of this line indicates that the test is valid .
With rapid home antigen tests, you can get results in 15 to 30 minutes. They all start with inserting the sterile swab from the kit (with the paper removed) into both nostrils and really rubbing your liner’s cocks for about 15 seconds each. No needles or pain, just uncomfortable, and no brain tissue removed. You put this in an included tube of fluid, which contains chemicals to break down the virus into its floating components. Then you drop (according to the instructions) the liquid into a well (small hole) of the cassette marked S for sample. In a different test, put the swab in a special place before closing the kit. The antibody-coated paper pulls the fluid along like a sponge, which is called capillary action.
If viral proteins are in the fluid, they will bind to the antibodies and a colored line will appear (more complicated chemistry) at the T mark. No line, no virus and a negative test. If a line appears, you assume you are infected with a virus. As the fluid passes through zone C, the control line lights up. If no line appears there, the test is invalid. Buy another kit (if you can find one). Sometimes the T line is weak. Many references say this still means the virus is in you. Others say it’s not likely. You need to correlate it with your symptoms.
The discussion of the interpretations of these different tests is really complicated (I seem to repeat this over and over again). Both tests rely on the presence of virus in the sample, the antigen test much more so. PCR amplifies viral genes so much that it can detect the virus long after you are no longer contagious. The home test is most helpful in deciding if you can pass the virus on to others. This makes the timing of the two tests crucial.
There are very few false positive results with antigen testing, but there is a large percentage of negative results due to collecting too early or too late for maximum viral load or quantity. If you test negative and you still have symptoms, the PCR test is next. Neither is perfect, but we have to “go with the flow”. The subtleties and nuances of their individual or sequential interpretation we will leave for another story. All home tests are of the lateral flow type.
They are worth employing when deciding what to do at social gatherings. All of our families have ecumenically agreed to use them before coming together for Christmas. We felt very positive about being negative. It made us feel as comfortable as possible enjoying our time together. Nobody got sick later either. We didn’t have to get worked up during our tests. It was worth the money and peace of mind.
Dr. Bures, a semi-retired dermatologist, has worked since 1978 in Winona, La Crosse, Viroqua and Red Wing. He also plays clarinet in the Winona Municipal Band and some Dixieland bands. And he appreciates a good pun.