New coronavirus nucleic acid test is usually based on the CT value of real-time fluorescence quantitative PCR to determine, different kits CT value range is different, usually between 30 and 40, usually less than the critical value of the determination of positive, more than the critical value of the determination of negative. CT value refers to the number of cycles corresponding to a certain amount of amplification of the starting template, which is also the critical value for determining negative and positive. Different kits have different critical values, generally between 30 and 40. If the CT value of the specimen is less than the threshold value, it will be judged as positive, and no CT value or more than the threshold value will be judged as negative. Real-time fluorescence quantitative PCR is an experimental method to replicate and amplify the RNA of the new coronavirus in the specimen, so as to find out the virus.The smaller the CT value, the higher the content of viral nucleic acid in the original sample; on the contrary, the lower the concentration.