With the new crown antigen test, the test is left for a long time (e.g., more than 24 hours), and in most cases the negative/positive result will not change. However, sometimes the original negative results of the test paper in the “T” will also appear a line, but at this time has exceeded the antigen detection reagent detection time (15 ~ 30 minutes after the addition of samples), this situation generally does not indicate that it is positive, but it is recommended to carry out a retest or nucleic acid test. The principle of the new crown antigen test paper is to use the test paper at the “T” attached to the specific antibodies against the new crown virus, when the sample contains a sufficient amount of new crown virus, the antigen on its surface will be specifically combined with the antibodies on the test paper, resulting in the test paper at the “T” red line signal. ” on the test paper. If the sample does not contain the virus, the test result will only show a bar at “C” on the test strip, and the test result will not change after a long period of time.