The study found that COVID-19 is a virus containing only ribonucleic acid (RNA), and the specific RNA sequence in the virus is a marker that distinguishes the virus from other pathogens.
At present, for the nucleic acid detection commonly used in the detection of COVID-19 patients, this method mainly uses real-time fluorescent RT-PCR and gene sequencing to test whether there is RNA of the new coronavirus in samples such as throat swabs of the tested person. If it exists, it means that it is infected by a virus.
Unlike nucleic acid testing, which aims to confirm whether the human body is infected with the new coronavirus at the time of testing, the main function of antibody testing is to confirm whether the tested person has ever been infected with the virus.
Antibody detection is very convenient, as long as you prick a drop of blood on your finger and smear it on the test paper, you can quickly know whether you have antibodies. Compared with the lengthy nucleic acid test, the antibody test is much faster.
Antibodies are mainly present in serum. Glycoproteins that are stimulated by antigens and can specifically bind to corresponding antigens and have immune function are called antibodies, also known as immunoglobulins (Ig). The most common function of antibodies is to neutralize toxins and prevent the invasion of pathogens. The principle of vaccines, as we all know, is to help the body to produce antibodies, so as to achieve the purpose of preventing diseases.
Antibodies can be divided into five classes: IgM, IgG, IgA, IgE, and IgD. The two most common antibodies in disease diagnosis and treatment are IgM and IgG. As the earliest antibody in the human body, IgM is the "pioneering force" of human anti-infection immunity; IgG is the antibody with the highest content in serum and body fluids, and is also the "main force" of anti-infection with high affinity, wide distribution in the body, and immune effect.
At present, antibody detection is mainly POCT detection and chemiluminescence detection of antigen methods. Antibody tests look in the blood for two types of antibodies, IgM and IgG, that fight various infections.
Blood tests for COVID-19 look for a protein specific to the new coronavirus that shows whether the body is making antibodies against it, rather than seasonal flu antibodies.
Under normal circumstances, IgM antibodies are produced early, and once infected, they are rapidly produced, maintained for a short time, and disappear quickly. A positive test in blood can be used as an indicator of early infection. IgG antibodies are produced late, last for a long time, and disappear slowly, and positive detection in blood can be used as an indicator of infection and previous infection.
Because COVID-19 is the first time it has invaded humans, there are no antibodies in anyone except the infected. Detection of antibodies combines the advantages of IgM for early infection diagnosis and the advantages of IgG for previous infection. Therefore, antibodies can provide important value for asymptomatic infections, including clinical diagnosis.