China CDC: Compared with antibody detection, nucleic acid detection is more sensitive.

  Cctv newsOn May 6th, the joint prevention and control mechanism of the State Council held a press conference on the disease control and prevention work of aiding Hubei.

  Zhang Xiaoguang, head of the testing team of China CDC in Huanggang, deputy director and researcher of Ceng Yi Institute of Viral Disease Prevention and Control of China CDC, said that after Covid-19 is infected with human body, it will first reproduce in the respiratory system, so it can be judged whether human body is infected with the virus by detecting the viral nucleic acid in sputum and nasopharyngeal swab.

  Zhang Xiaoguang pointed out that after a period of infection, usually 7-10 days later, the human body will produce specific antibodies against the virus. IgM antibody appears first, then IgG antibody will appear, so the immunological detection method can detect these specific antibodies and judge whether the human body has been infected with the virus.

  Zhang Xiaoguang introduced that the difference between the two is that the positive nucleic acid indicates the existence of viral nucleic acid in the specimen, which means that the infected person may be contagious. IgM antibody positive indicates that the patient is in the early stage of infection, while IgG antibody positive indicates that Covid-19 has been infected, but it is not certain whether it is contagious. For example, recovered people are generally positive for IgG antibody. If the nucleic acid test is negative, the nucleic acid is still negative after 24 hours, which indicates that it is not contagious. Compared with antibody detection, nucleic acid detection is more sensitive, and it is also the "gold standard" for laboratory detection. Of course, both antibody detection and nucleic acid detection have a certain proportion of false positives and false positives, so clinicians should make comprehensive judgments based on clinical symptoms and epidemiological investigation results.