The probability of false-negative tests is related to sampling and mixing factors. Because the new crown antigen test needs to be self-tested, including the entire sampling and experimental steps, because not all people can do standardized operation, thus causing the probability of false negative is relatively large. The first is sampling, according to the operational requirements need to be in both nostrils deep 1 ~ 1.5 cm, self operation may not be able to fully achieve due to discomfort, but also requires a stay of 15 seconds, but also an important indicator of the effectiveness of sampling. In addition, after the sampling is completed, it needs to be put into the test tube and mixed with the solution for 30~40 seconds, otherwise it will not be able to react completely. Some people are unable to mix for enough time when testing on their own, resulting in failure to accurately detect, which is also an important reason for false negatives. If in doubt, it is recommended to go to a designated place for nucleic acid testing to confirm the diagnosis.