China News Service, Beijing, July 1 (Chen Hang) The Beijing Municipal Government Information Office today held the 138th routine press conference for epidemic prevention and control. For the diagnosis of a patient after two negative nucleic acid tests, the Chinese Center for Disease Control and Prevention Wu Zunyou, chief expert in epidemiology, said that at present, nucleic acid detection and antibody detection are two different components of the body. The former detects viral nucleic acids and the latter detects antibodies. The detection of nucleic acid is to check whether there is a viral nucleic acid component in the nasopharynx. If it is positive, there is an infection. Antibodies are substances that reflect the body's immune response to viral infections. The time is generally two weeks after infection. Not only can antibodies be detected after an infection, but to reflect the status of infection from two different perspectives.
Wu Zunyou introduced that it is normal for individuals to have no antibodies at an early stage, and it is normal for antibodies to be tested negative. After the nucleic acid test was negative, the possible reasons are as follows: First, the virus is infected in the lungs. The sampling is usually in the nasopharynx or pharynx. The secretion produced by the disease blocks the airway of the lungs. The amount of virus in the pharynx is very large. Less, not necessarily at this time. The second is that the sampling is not in place and the quality is not high. The third is the change of the patient's condition after being infected with the virus, and the sampling period will affect the sampling quality.
Wu Zunyou said that the above three conditions may cause a negative test and later a diagnosis. This condition is generally clinical, but it is relatively rare. This involves how to interpret the laboratory test results. For a person who has been in contact with a patient or has visited a high-risk area and has symptoms, even if the nucleic acid test is negative, it cannot be taken lightly. At this time, we cannot rely on nucleic acid detection alone, but combine it with epidemiological history and clinical symptoms. If a person does not go to a high-risk area and does not have close contact with an infected person, a negative nucleic acid test is safe.