Antigen testing is generally referred to as Neocoronavirus antigen testing. If there is no visible line, or only a line at the “T” line, the result is invalid and a new test card is required. Neocoronavirus antigen is detected on a test strip by the combination of an antigen and an antibody, and there are three types of results: positive, negative, and invalid. If there is no visible line, or only a line at the “T” line, the result is invalid. Many factors can lead to invalid antigen test results, such as improper preservation of the test kit, insufficient amount of liquid added to the droplet, sampling swabs are not in place or contaminated can occur antigen test invalid, so the test should be strictly in accordance with the instructions for the test, to avoid invalid results. Invalid antigen test results require retesting or other nucleic acid tests or related investigations. Antigen testing is not a substitute for nucleic acid testing and can only be used as a rapid test.