What is nucleic acid testing?
What is nucleic acid testing?
Nucleic acid testing is a technique used to detect nucleic acid sequences on genetic material (RNA or DNA), typically to detect and identify certain organisms, such as viruses or bacteria. The principle is that each organism's genetic material has its own specific sequence, which distinguishes it from other organisms.
The nucleic acid detection substance is the nucleic acid of the virus. Nucleic acid testing is to find out whether there is nucleic acid of foreign invading viruses in patients' respiratory specimens, blood or feces to determine whether they are infected with the new coronavirus. Therefore, once the nucleic acid is detected as "positive", it can be proved that the virus exists in the patient.
Principle of nucleic acid testing
All organisms contain nucleic acid, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The novel coronavirus is a virus that contains only RNA. The specific RNA sequence in the virus is a marker to distinguish the virus from other pathogens. After the emergence of the novel coronavirus, Chinese scientists completed the analysis of the entire genome sequence of the novel coronavirus in a very short period of time, and found the specific nucleic acid sequence of the novel coronavirus by comparing it with the genome sequences of other species. During clinical laboratory testing, if the specific nucleic acid sequence of the novel coronavirus can be detected in the patient's sample, it should indicate that the patient may be infected with the novel coronavirus.
The most common method to detect the specific sequence of the novel coronavirus is real-time quantitative PCR (polymerase chain reaction). Since the PCR reaction template is only DNA, the novel coronavirus nucleic acid (RNA) should be reverse transcribed into DNA before the PCR reaction. In the PCR reaction system, a pair of specific primers and a Taqman probe are included, and the probe is a specific oligonucleotide sequence, and the two ends are respectively labeled with a reporter fluorescent group and a quenching fluorescent group. When the probe is intact, the fluorescent signal emitted by the reporter group is absorbed by the quencher group; if there is a target sequence in the reaction system, the probe binds to the template during PCR reaction, and DNA polymerase uses the exonuclease activity of the enzyme along the template to separate the probe. Enzymatic cleavage is degraded, the reporter group is separated from the quencher group, and fluorescence is emitted. Each time a DNA strand is amplified, a fluorescent molecule is produced. The fluorescence quantitative PCR instrument can monitor the number of cycles (Ct value) that the fluorescence reaches a preset threshold value, which is related to 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.
Application of nucleic acid testing
Since the outbreak of the novel coronavirus, nucleic acid testing has played a huge role as the "gold standard" for whether or not to be infected with the novel coronavirus. Since the amount of genetic material is usually small and difficult to detect, it is necessary to replicate the genetic material by means of polymerase chain reaction during nucleic acid detection. This nucleic acid detection is also known as nucleic acid amplification detection.
After the novel coronavirus infects the human body, it will first multiply in the respiratory system, so it can be determined whether the human body is infected with the virus by detecting the viral nucleic acid in sputum and nasopharyngeal swabs. Therefore, a positive nucleic acid test can be used as a new standard for the diagnosis of novel coronavirus infection.
Manufacturer of Nucleic acid extraction
Geneture medical specialize in nucleic acid extraction, provide the whole set products for Covid-19 test, include Nucleic acid extractor, extraction kits, PCR analyzer and detection reagents. Don’t hesitate to contact with us for more details.