There has been some troubling information breaking involving the Federal Government’s statistics on testing.
As of today, the government has reported that over 13 million tests have been “given”.
Let’s take a look at that number to better understand it.
THE NUMBER OF TESTS IS NOT THE SAME AS THE NUMBER OF PEOPLE TESTED
The first thing to remember is that we have been, so far, testing predominantly the severely ill patients only. The purpose, as I have continually pointed out, is to allow for the screening of patients entering the hospital to know how to segregate them and how to protect the healthcare workers. There are others tested at the same time, generally spouses and close contacts of those patients, but the majority are those presenting with symptoms that suggest severe disease.
The next thing to remember is that a patient that tests positive is tested multiple times before they are released from the hospital. There need to be at least 2 negative tests on separate days before release is allowed.
Also, in many locations (the White House is a great example), the same people are tested on multiple separate days.
The net result of these processes is that the 13 million tests performed is not representative of the number of individuals tested. The number of people tested is only a fraction of the number of tests given.
THE NUMBER OF TESTS “GIVEN” IS NOT THE NUMBER OF TESTS FOR VIRUS
The disturbing news recently reported is that the 13 million tests given is NOT the number of tests for virus, it is a summation of ALL tests done, both for the virus and for antibodies. These two types of tests are so profoundly different, both in what they test for and what they are used for, that grouping them together is not only inappropriate but misleading and inaccurate.
It is, perhaps proper for us to review the different tests being done, what they determine and how the results are used. There are two basic types of tests, one tests for the presence of virus, one for the presence of antibodies to the virus.
TESTING FOR THE VIRUS
The idea that we test for virus is actually inaccurate. To test for virus, we would take a sample of blood, or lavage (fluid from the nose, the throat or the lungs) from a patient and then attempt to infect either another animal or, more usually a tissue culture with that sample. The presence of new detectable virus in that tissue culture would positively indicate that there was infectious virus in that patient. This test is the most definitive, but is very, very seldom done. It is difficult, expensive and requires a lot of laboratory personnel. For our discussion this testing method is effectively nonexistent.
PCR testing. This is the predominant, if not the sole method for testing for the presence of virus. We have gone into this in detail before, but basically it is a way to look for the existence of RNA fragments specific to the virus. When those fragments are found, we know that the patient has virus in his/her system. We don’t know if these patients are still contagious because it is still theoretically possible that after the immune system has cleared the virus, because the immune system primarily reacts against the proteins, not the genetic material, that there may still be pieces of RNA within these patients even when there is no intact virus particles.
What do we do with this information?
If one tests positive for virus they need to be isolated immediately. If the disease process is advanced, they need to be hospitalized. If there are mild or no symptoms, they need to be isolated at home. All contacts need to be identified and tested themselves to determine whether the infection had been spread beyond the individual identified.
If one tests negative, simple safety and health precautions should continue. If the negative patient is still ill, the illness is probably from another vector and treatment would be modified appropriately.
TESTING FOR ANTIBODIES
There are almost 100 different tests being promoted on the market to test whether you have antibodies present in your system. Most have not been approved by the FDA, although the FDA has allowed them to be marketed based on the manufacturer’s own validation.
There again are two types of antibody tests.
The first one, and the best, tests for the presence of “neutralizing” antibodies, the types of antibodies that will most likely protect you from infection. We do not know now, nor will we know for over at least a year, whether antibody responses with neutralizing antibodies prevent an individual from getting infected. We have good reason to hope that they will; that is why we are working on getting a vaccine. But, as we have spoken about in the past, there are viral diseases that stimulate strong immune responses that are not protective, notably HIV/AIDS.
The second one, and most common, simply tests for the presence of antibodies that can bind to a virus particle. This may sound like a subtle difference; however, it is not. It is very significant. If you have produced antibodies to the virus, but those antibodies are not neutralizing, then you have very little protection against subsequent infection, even if you have been previously infected and have recovered.
What do we do with this information?
This is the crux of the issue.
If you test positive for antibodies, what does it mean? If those antibodies are neutralizing, it is good evidence that you have had and have recovered from the infection. You are potentially safe from being infected again; however, you are not shielded from the virus. It is still possible that virus could get into your system; if it does, the antibodies will, presumably prevent you from getting ill. But if virus has entered you nose or mouth, it can still be distributed to other people for some period of time until it is cleared from your system. So, you need to be cautious in public.
If the antibodies detected were from a test that is more general, then you do not know if you actually had been infected. It remains possible that there are some antibodies to proteins on the virus surface that were generated from a previous coronavirus (non-COVID-19) infection. So, these tests will not provide any information to you about how to change your actions.
Finally, just because you have antibodies, it does NOT mean that you are clear of virus. You may still be shedding virus even if you have generated a strong immune response. The two curves overlap.
If you test negative for antibodies, then you are no further advanced than before. There is nothing you should do to change your lifestyle.
WHY DO ANTIBODY TESTING?
The answer here is that on an individual basis there is little if any value to being tested. There will be companies advertising services, tests, etc. They will charge varying amounts. The tests are reasonably inexpensive to administer and the equipment to do the tests is simple and easily obtained. Therefore, the profit motive to convincing you to get tests is high. The results are pretty useless.
The antibody tests though, have tremendous value in epidemiology. If you test a wide group of the population, you can get a good estimate of how many people have been exposed to virus. Most importantly, if you re-test that same population a week or two later, you can get an extremely valuable indication about whether the infection is stable or expanding.