What is the difference between negative and positive for the new coronavirus?
@jacker What is the difference between negative and positive for the new coronavirus?
In the process of clinical testing, the test results are usually expressed by negative and positive, with positive representing abnormality and lesions, and negative representing normal. A negative test for the new coronavirus means that a person does not have the coronavirus in his body and has not been infected with the coronavirus before. The positive means that there is currently or has been infected with the coronavirus in the human body.
Novel coronavirus negative usually refers to the time when the patient's throat swab, sputum or blood is negative for the new coronavirus nucleic acid test, and sometimes the respiratory secretion or blood can also be negative for the new coronavirus gene sequencing. , the patient may not be infected with the new coronavirus. However, this experiment has a certain false negative effect, and some patients need to undergo multiple tests to become positive.
Some patients also need to pass the epidemiological history, that is, when the patient has recently traveled to an epidemic area or contacted a patient who may be infected, and the lung CT has changes in viral pneumonia, a preliminary judgment can also be made at this time. form. Therefore, clinical diagnosis of new coronavirus infection is usually based on the detection of new coronavirus nucleic acid, combined with clinical symptoms, past history, and chest CT.
How to easily and quickly test the negative and positive of the new coronavirus?
China is currently doing a very good job in the detection and prevention of the new coronavirus. China has produced a steady stream of rapid test kits and Infectious Disease Portable Test Sampling Booth. The instrument engineer of QINSUN said that a new generation of nucleic acid testing booths is currently under development and will be provided to the world in the later stage. market!
Why are nucleic acid test results falsely negative?
Cheng Jing, an academician of the Chinese Academy of Engineering and a chair professor of the Department of Biomedical Engineering at Tsinghua University, said that this may be caused by a variety of factors. "First of all, the development of the kit requires more than a dozen key chemical raw materials, such as enzymes and synthetic DNA. Different companies choose different suppliers of raw materials, and the activity of enzymes and the purity of DNA will vary, which will affect nucleic acid detection reagents. accuracy." Cheng Jing said.
"In the process of product development of the kit, the preparation of raw materials, the selection of production processes, the ability of R&D personnel, and the use of technical means may cause deviations in every link, and the accumulation of errors will also lead to differences in the sensitivity of kit products." Cheng Jing Say.
Furthermore, the irregular sampling process will also affect the subsequent separation and determination results. Taking the most common and easy-to-use throat swab collection as an example, due to the low content of the new coronavirus in the throat, it may cause missed detection. "Although it is only a few strokes with a cotton swab in the pharynx, if there is no good professional practical skills, the sample collection site and method may not meet the specifications, which may directly affect the test results." Cheng Jing said, in addition, just infected of patients may also have negative test results due to the limited amount of the virus in their bodies.
Cold chain transportation must be adopted when sending samples. If the samples are damaged during transportation, the test results will also be affected.
The problem of false negatives in nucleic acid testing once triggered calls to use CT images instead of nucleic acid detection reagents to diagnose new coronary pneumonia. In the "Diagnosis and Treatment Plan for Novel Coronavirus Infected Pneumonia (Trial Version 5)" recently released, a "clinically diagnosed case" was added in addition to "suspected cases" and "confirmed cases", and "suspected cases with pneumonia" were added. Image features" as its diagnostic criteria (limited to Hubei Province), which also means that CT imaging results have become the basis for "clinical diagnosis cases".
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