If The Pcr Test Is Negative, Can I Get Coronavirus

2021-02-13   |   by CusiGO

The first thing you need to understand is that PCR detects the genetic material of coronavirus, its RNA, and it can measure the number of viruses in an organism, that is, the viral load. What does PCR negative mean? This means that at the time of sampling, the test did not detect the virus in our bodies. There may be two reasons for this, either you don’t have a virus, or the viral load is too small to detect. I mean, this negative doesn’t mean we can’t get infected after we get the sample. This can happen even after sampling. If the cause of negative detection is a certain viral load, but the viral load is too low, PCR can not detect the viral load, there may be many reasons. What may happen is that the person being sampled is infected very early, and the viral load may increase after a few days, and it can already be detected. It may also be undetectable because the immune system has attacked and defeated the coronavirus.

In the case of antigen testing, it’s also used to detect if we’re infected. The goal of this test is to cover the proteins in the genetic material of the virus, like the coat of the virus. Like PCR and RNA, if you have these proteins in your body, it’s because you have coronavirus. In this case, it’s exactly the same as PCR. Negative means that it was not infected at the time of sample collection, or the viral load was too low for the test to detect it. Moreover, this is more likely to happen in this test because it is less sensitive than PCR. That is to say, PCR can detect less virus than antigen. But the reason why the antigen test is negative is the same as the reason why PCR is negative: either you don’t have the virus, or the viral load is too low for the test to detect it, or you are in the early stage of infection, or your immune system has successfully defeated it.

In both cases, if the result is positive, the subject carries the virus.

The antibody test is a completely different test because it shows our immune response to coronavirus. There are two options. This test can detect IgM, which is a rapid response immunoglobulin. As the name suggests, this is the protective effect of our body when it detects the virus. When the IgM test is positive, it means that the infection is in progress. But the antibody test can also detect IgG, which is a slow response immunoglobulin, produced at the end of the infection or at the end of the infection, is to produce long-term immunity immunoglobulin. IgM positive means that the virus is most likely in your body. IgM negative means that at the time of collection, you were not infected, that is, you did not have coronavirus. IgG negative means you’re either not infected, or because the defense mechanism of the recent delayed immunoglobulin response hasn’t been activated. In other words, the antibody test measures your immune response to the virus, as well as the time you have been infected with the virus, whether it is in progress or has passed.

Elena senis Herrero is a researcher at the Vall d’Hebron Cancer Institute

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