As the global pandemic continues, many, including me, are wondering what kinds of tests the scientific community have produced to help identify people infected with Covid-19. One of these types of tests typically used are antibody response tests. These can tell us a number of things, including if you have been infected in the past or are in a current infection. By analyzing antibody titers, scientists and doctors can obtain information on the amount of each type of antibody a patient has produced. Having only IgM antibody titers typically indicates a T independent response to pathogens, since no antibody class switching has occured yet. Having both IgM and IgG antibody titers can indicate that the patient is in a current infection or recovering from one since these are produced by the adaptive immune system upon invasion. Having primarily IgG titer suggests that the patient’s immune system has activated a secondary response, indicating that they have already seen this pathogen before. If we could determine who was IgG positive, we could detect asymptomatic people and prevent them from spreading infection unknowingly.
One of the Covid- 19 tests that is being circulated now is a serology test that is being used to try to quantify the number of cases, including those that are asymptomatic or have recovered. According to an article published by Johns Hopkins Bloomberg School of Public Health, serology tests are blood based tests that can be used to identify whether people have been exposed by looking at their immune response. There are many serology assays, of which the most common one being used is the rapid diagnostic test (RDT). These tests use blood samples to test patients for antibodies IgG and IgM, or viral antigen. It is recommended in this test to have baseline (before infection) numbers of IgG and IgM titers in order to see how much they have increased by.
Additionally to antibody tests, there are RNA tests that are being used to tell if someone is infected with Covid-19. An article published in American Society for Microbiology states that most Covid-19 tests identify viral RNA through nucleic acid amplification, using PCR. These tests have to have to have viral RNA present in the sample and so they are generally taken from the nasopharynx and oropharynx. Following swabbing, the samples are placed into a liquid to release virus RNA from the swabbed solution. This viral RNA is extracted and then amplified. This article also states that true clinical sensitivity of any of these tests are unknown, so a negative test does not negate the possibility that the individual is infected. They also point out that detected of viral particles does not equate to living virus that can be transmitted from that patient. These acute illness tests can be very useful but also have pitfalls that healthcare providers must be aware of. In my opinion, it would be more useful to know more basic information about the virus more broadly which not many people know, especially not the public.
Microbiology, Get Cultured! 