Experts responded that the patient was diagnosed despite negative nucleic acid and antibody test results! What exactly happened? Attached are the detailed reasons!

Everyone knows that the only way to detect the new coronavirus is to conduct a nucleic acid test, but some people are listed as confirmed even though the test results are negative. What exactly happened? Recently, experts responded that the patient was diagnosed despite negative nucleic acid and antibody tests. What was the specific reason for this?

1. Experts respond. What is the specific situation of being diagnosed even though the nucleic acid test and antibody test are negative?

On the afternoon of July 1, the 138th press conference on the prevention and control of the new coronavirus pneumonia epidemic in Beijing was held. A reporter asked, why did the results of two nucleic acid and antibody tests for some cases being negative before they were confirmed?

Wu Zunyou said that it is normal for the antibody to be negative. There are several situations in which the nucleic acid test is negative:

1. First, after infection with the new coronavirus, the virus is mainly in the lungs, and sampling is mainly done in the nasopharynx. If the virus is in the lungs, the secretions produced by the lesions will block the lungs, and the amount of virus in the pharynx is very small, so it may not be possible to collect it.

2. Secondly, the sampling may not be done properly, the quality may not be high, and some viruses may not be collected.

3. Third, the course of the patient's illness changes after infection, and the sampling period will also affect the quality of sampling.

The above three situations may result in a confirmed diagnosis even though the test result is negative, which is relatively rare in clinical practice. If a person has been in contact with a new coronavirus patient, has been to a high-risk area, and has clinical symptoms, a negative test result cannot deny his or her infection. If a person has symptoms and an epidemiological history, but the result is still negative, repeated sampling and testing are required. Whether a person is infected cannot be determined solely by laboratory tests, but must be based on a combination of epidemiological history and clinical symptoms. If a person has not been to a high-risk area and has not been in contact with a case, a negative test should be safe at this time.

2. Why is the validity period of nucleic acid test set at 7 days?

Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, said at a press conference on the 1st that the shorter the validity period of ideal nucleic acid testing, the safer it is. However, if the time is too short, the testing frequency will be too high, making actual operation difficult. The validity period of nucleic acid testing is set at 7 days, which is mainly based on the virus transmission pattern, especially the length of the incubation period. The incubation period after viral infection is usually 3-7 days, and sometimes as long as 14 days. Therefore, the quarantine period is limited to 14 days and the validity period of the nucleic acid test is set at 7 days.