Is nucleic acid detection sensitivity affected by virus mutation?
Nucleic acid detection is a mature and internationally accepted laboratory diagnostic method. The nucleic acid detection method is highly sensitive, and the specificity can reach 100% in terms of methodology. That is to say, the positive result of nucleic acid test is equivalent to the result of pathogen culture and becomes the “gold standard” for diagnosis.
For the nucleic acid detection of the new coronavirus, the nucleic acid detection reagents used are aimed at the double-target or triple-target genes of the new crown. There is basically no possibility that the virus mutation will mutate in two or three target genes at the same time, so the virus mutation has no ability to detect nucleic acid detection. what impact. Judging from the national inter-laboratory quality evaluation results of the National Health Commission’s Clinical Laboratory Center for Delta and Omicron variants, as well as the practical application during epidemics across the country, the current nucleic acid detection can be effectively detected, which also proves that this a little.
What factors will affect the sampling results?
Specifically, the factors that affect throat swab sampling mainly include the following five aspects: one is the depth of throat swab collection, the second is the time of contact with the mucous membrane, the third is the intensity of sampling, and the fourth is the relationship between the sampler and the sampled. The height difference between the five is the degree of cooperation of the collected people in the collection process.
When participating in nucleic acid testing, it is necessary to actively support and cooperate with the sampling personnel, and standardize the coordination of sampling according to their on-site requirements to ensure the sampling effect.
Does nucleic acid detection sampling swab have any negative effects?
Sampling swabs are not cotton swabs. They are made of polyester or nylon fibers, which are similar to toothbrushes in daily life. Sampling is like brushing your teeth with a toothbrush, but it brushes the back wall of the pharynx in the mouth to take cells, and then puts the sampling swab into the sampling tube.
Sampling swabs belong to medical devices. The production environment and requirements are very strict. There are also relevant standards for quality supervision. There will be some stimuli during the sampling process, and different people feel different. For example, some people’s pharynx is more sensitive, they feel uncomfortable after sampling, feel a foreign body, they will feel itching or vomiting, and some people will be more tolerant. Individual differences are large.
In another case, the mouth is usually opened when sampling, and some people put the base of the tongue together with the soft palate. If the sampler wants to ensure the quality of the sampling, he will probe inside, looking for the posterior pharyngeal wall and tonsils. There is stimulation, and some people have a very strong response to stimulation, such as vomiting and coughing, but it is easy to relieve once the sampling is completed. So sampling is not harmful to the individual.
Does a positive nucleic acid test environmental sample mean that the environment is infectious?
The detection of positive nucleic acid in environmental samples does not mean that there must be live viruses in the environmental samples. To identify whether there is live virus, cell virus isolation must be performed, or virus isolation in sensitive mice to determine whether there is live virus.
Whether it is a dead virus or a live virus, nucleic acid is contained in environmental samples, and nucleic acid testing can be positive. Therefore, a positive nucleic acid detection does not mean that it has a live virus, and comprehensive research and judgment is required.
When testing environmental samples, we must pay attention to the source of nucleic acid testing samples. If it comes from the vaccination site, because the vaccine used at the vaccination site is an inactivated vaccine prepared from complete virus particles, this vaccine has complete viral nucleic acid, and the nucleic acid test will be positive, which is why the cotton swab at the vaccination site must not be used. Just throw it away. Therefore, if a positive test is detected in this environment, there is a high probability that it is the nucleic acid of the inactivated vaccine. This kind of nucleic acid removal operation does not mean that there is a live virus. If a positive nucleic acid is detected in an environmental sample, it can be simply understood that there is nucleic acid of the new coronavirus, but whether there is a live virus or not requires a very strict judgment.