Antigen testing is the detection of the proteins of the viral capsid, which is diagnosed by combining antigen and antibody to form a complex that is color-coded. Viruses are composed of two parts, the “core” and the outer shell, the “core” is the nucleic acid of the virus, and the outer shell is the protein of the virus, which is also known as the antigen. Antigen detection is to directly use the virus shell for detection, through the virus protein antigen matching antibody, through a special operation process to make the two combined, forming a complex, the complex will be special color, thus helping diagnosis. In summary, antigen testing is the detection of the outer shell of the virus, i.e., the protein component, but this test may result in false positives, and nucleic acid testing is required if necessary.