Since the New Coronavirus outbreak, I am sure we have all experienced "nucleic acid testing". Nucleic acid testing plays an extremely important role in the diagnosis of NCCV infection. Not only can it identify asymptomatic patients in the incubation period as much as possible, but it can also greatly reduce the risk of transmission.
What is the principle of nucleic acid testing?
Because nucleic acid is the genetic factor of a virus, it is a large chain of 4 nucleotides, with different molecules representing different nucleotides and forming a long chain. Nucleic acid testing is done by detecting a segment of the chain that is unique to the New Coronavirus and not found in other viruses.
The material used for nucleic acid detection is the nucleic acid of the virus. The current detection technology is mainly through PCR (polymerase chain reaction) technology to detect the nucleic acid of the virus. Detection, the nucleic acid chain of the new coronavirus as the detection target, through PCR amplification of the segment of the target gene sequence, combined with the prior addition of a segment of fluorescent labeling probe on the detection reagent, which in turn generates a fluorescent signal.
The nucleic acid test is, to put it bluntly, to determine whether a sample contains nucleic acid molecules of the new coronavirus by detecting the intensity of the fluorescence signal response. In samples containing viruses, the stronger the fluorescent signal response. In contrast, in those that do not contain viral factors, the target genes are not amplified and no enhancement of the fluorescent signal is detected.
Therefore, nucleic acid testing can monitor the genes of the virus and provide timely warning, which is important for epidemic preparedness. Pharyngeal swabs are a common form of nucleic acid testing, but two other types of testing should also be known.
Each of the 3 forms of nucleic acid testing has its own advantages
Pharyngeal swab test
This is the most commonly used form of testing and the one that is often used. During the sampling process, the patient opens his or her mouth and makes an "ahh" sound, and the testers use a sterile cotton swab to gently and quickly swab the lateral and posterior pharyngeal walls of the subject several times.
Pharyngeal swabs are often used in the testing process because they are easier and faster to collect and more acceptable to the public, but the risk of exposure is also greater.
Nasal swab testing
In this type of testing, a test swab is inserted vertically into the nostril. And the swab is gently rotated and left in the nasal cavity for about 15 seconds to perform the test.
Compared to pharyngeal swabs, nasal swab testing is more accurate for less experienced testers and the risk of exposure is lower in this way. However, it is less suitable for some nasal allergy patients, hypertensive patients and those who are on long-term anticoagulation as well as antiplatelet.
At this point, one might ask, "Which is more accurate, nasopharyngeal swabs or oropharyngeal swabs?" In fact, at this stage, we have a mature process protocol for either type of test. It is just that compared to nasopharyngeal swabs, oropharyngeal swabs are more acceptable and the speed of collection is easier and faster.
Anal swab test
This is a test in which a test swab is inserted into the anus and a sample is taken in the folds of the anus or at 2 to 3 cm for neocoronavirus testing.
Many patients reject anal swab testing, but anal swabs can improve the accuracy of testing for people with new coronavirus infection to some extent. It is true that there is a subset of patients who test negative for pharyngeal swabs but show a positive test by anal swabbing. There are some patients who are negative for the other two tests and still have a positive anal swab.
Each of the three nucleic acid testing methods has its own advantages and disadvantages, and you can choose the one that is more suitable for you.
