Nucleic acid was tested just a few days ago, why do I need to test again?
Since the new pneumonia outbreak
The term "nucleic acid testing" has become a household word
But in recent reports from around the world
"confirmed cases have tested negative for nucleic acid multiple times"
are commonplace.
What's going on here?
Why do multiple tests test positive?
The detection rate of the first nucleic acid test after any virus infection cannot be 100%, and the new coronavirus is no exception, there are many factors that lead to a negative test early and a positive test later.
1, virus detoxification level impact
Detection results are mainly influenced by the level of virus detoxification in the patient's body. Some of the new crown cases, especially asymptomatic infected, early detoxification level is not high, the body virus concentration is very low, more than the detection limit of the detection kit, resulting in the inability to detect positive, and with the passage of time, the virus in the body detoxification level continues to increase, in the late sampling and testing is positive.
2, related to the course of the disease
Earlier, in the program "News 1+1", Feng Zijian, deputy director of the Chinese CDC, said that this phenomenon: the infected person from the infection of the virus to the beginning of detoxification, professionally called "strong hidden period", and asymptomatic infected person from the infection of the virus to the beginning of detoxification, professionally called "pre-hidden period "It can also be called the window period for laboratory testing and screening. During the window period, the test may not detect positive many times, but will detect positive at the end of the pre-cryptic period, "this phenomenon is completely understandable".
3, other factors
Test results are also affected by other factors, such as sampling sites, sampling volume, sample preservation, transport conditions, and the sensitivity of the detection reagents. However, in order to guide medical institutions to do a good job in nucleic acid testing of new coronaviruses, the state issued the "Workbook for New Coronavirus Nucleic Acid Testing in Medical Institutions (for Trial Implementation)" to further standardize the work of technicians, specimen collection, specimen management, laboratory testing, and result reporting for nucleic acid testing of new coronaviruses, to ensure the quality of testing and improve the efficiency of testing.
Why multiple testing?
From the perspective of collection, whether a pharyngeal swab or a nasopharyngeal swab is collected, not necessarily 100% of positive specimens are collected. From an experimental perspective, the first round of nucleic acid testing may lead to false negatives and can miss some positive patients. From the perspective of disease progression, not all viruses are collected during progression, and some may be in latent phase.
Can a missed diagnosis occur?
According to the Novel Coronavirus Pneumonia Treatment Protocol (Trial Version 8), interpretation of nucleic acid test results cannot rely solely on laboratory results, but must be combined with clinical manifestations and/or epidemiologic history, etc. for a comprehensive judgment. If there is a clear epidemiological history and clinical symptoms, even if the nucleic acid test is negative, it cannot simply be judged as uninfected. In addition, new crown-specific antibody (IgM, IgG) tests can be a useful supplement to screening for suspected patients.
In addition, "false negative" cases, which occur after multiple negative tests, are usually found in high-risk areas and in populations in priority areas. When an outbreak is detected in a key area, the key population is isolated and observed at the first opportunity. There is no need to panic!
After the emergence of cases
To improve the accuracy of testing
Repeated multiple rounds of testing are more necessary
Therefore, I suggest
If you receive an SMS notification
Nucleic acid testing is needed again
you must listen to the arrangement!
