Views:5 Author:Site Editor Publish Time: 2020-04-20 Origin:Site
The new coronavirus pneumonia outbreak at the end of 2019 affects the hearts of the people in the country. In this battle without smoke, how to detect and treat early, improve the ability of treatment and reduce the spread of disease, the new coronavirus detection reagents play an important role, then What is the principle of virus detection?
There are usually two strategies for detecting infectious diseases: detecting the pathogen itself, or detecting antibodies produced by the human body in order to resist the pathogen. Detecting pathogens can detect antigens (generally pathogen surface proteins, some internal nuclear proteins), as well as nucleic acids. If any of antibody, antigen or nucleic acid is detected in the patient's body fluid, it means that it has been infected. Because antibody production takes time, usually ranging from a few days to several weeks, some patients with weakened immune function may have a low antibody volume, which is likely to cause false negatives (already infected, but the test results do not appear to be infected). At the beginning of infection, the pathogen antigen content is also low, which is also not easy to detect. Therefore, the detection of nucleic acid sequences of pathogens is widely used at present, and the signal is amplified by the amplification reaction. The detection has high sensitivity and good specificity.
All organisms contain nucleic acids except prions. Nucleic acids include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The new coronavirus is a virus containing only RNA. The specific RNA sequence in the virus distinguishes the virus from other pathogens. Markers. After the emergence of the new coronavirus, Chinese scientists completed the analysis of the whole genome sequence of the new coronavirus in a very short time, and found the specific nucleic acid sequence in the new coronavirus by comparing with the genome sequence of other species. During clinical laboratory testing, if the specific nucleic acid sequence of the new coronavirus can be detected in the patient sample, it should be prompted that the patient may be infected by the new coronavirus.
A common method for detecting new coronavirus specific sequences is fluorescence quantitative PCR (polymerase chain reaction). Because the PCR reaction template is only DNA, the new coronavirus nucleic acid (RNA) should be reverse transcribed into DNA before the PCR reaction. In the PCR reaction system, it contains a pair of specific primers and a Taqman probe. The probe is a specific oligonucleotide sequence, and the reporter fluorescent group and the quenching fluorescent group are labeled at both ends. When the probe is complete, the fluorescent signal emitted by the reporter group is absorbed by the quenching group; if there is a target sequence in the reaction system, the probe is combined with the template during the PCR reaction, and the DNA polymerase uses the exonuclease activity of the enzyme along the template The enzyme is degraded, and the reporter group is separated from the quenching group, which fluoresces. Every time a DNA strand is amplified, a fluorescent molecule is produced. Fluorescence PCR instrument can monitor the cycle number (Ct value) of fluorescence reaching a preset threshold and the concentration of viral nucleic acid. The higher the concentration of viral nucleic acid, the smaller the Ct value. The products of different manufacturers will determine the positive judgment value of this product according to the performance of their own products.
Kit testing The results can confirm the role of clinical diagnosis. As a typical device for diagnosing pneumonia, mobile DR can quickly complete digital photography examinations of the chest and other parts of the whole body. It is a reliable basis for the detection of new coronavirus infection pneumonia. Welcome to call us.