1, what is nucleic acid detection?
Nucleic acid detection is to collect cells from specific parts of human body, and use in vitro amplification technology to detect whether they contain COVID-19 RNA nucleic acid, so as to confirm whether human body is infected. Nucleic acid detection is the most reliable method to find asymptomatic infected people and potential sources of infection, and it is the first measure to implement the "four early" measures.
2. How to choose the sampling point for nucleic acid detection?
After the human body is infected with COVID-19 virus, the virus enters the throat through the nasal cavity and oral cavity, then reaches the trachea and bronchus, and then reaches the alveoli. Therefore, the main samples collected for nucleic acid detection in COVID-19 are nasopharyngeal swab and oropharyngeal swab of upper respiratory tract, alveolar lavage fluid, bronchial lavage fluid, nasopharyngeal or respiratory tract extract and deep sputum of lower respiratory tract. The detection rate from high to low is alveolar lavage fluid, deep sputum excretion, nasopharynx and oropharynx. From the convenience of sampling and the comfort of patients, oropharyngeal swab and nasopharyngeal swab are more suitable for large-scale nucleic acid collection. Alveolar lavage fluid is generally aimed at critically ill patients because of its complicated operation.
3. Why do some people collect nasopharyngeal swabs and some people collect oropharyngeal swabs?
According to different people and different needs, the sample collection methods will be different. Key populations such as asymptomatic infected persons, entry personnel and close contacts should collect nasopharyngeal swabs for nucleic acid detection during isolated observation. Compared with nasopharyngeal swab, oropharyngeal swab is faster, simpler and easier to collect, and the detection rate can meet the requirements. Therefore, when nucleic acid detection is carried out in low-risk areas, oropharyngeal swabs are often collected.
4. How to collect qualified oropharyngeal swabs?
Collecting qualified oropharyngeal swab samples is one of the key steps to ensure the accuracy of nucleic acid detection results. When collecting oropharyngeal swabs, the sampler must open his mouth and fully expose the tonsils and posterior pharyngeal wall on both sides of the mouth, so that medical staff can accurately sample. When some people's mouths are not wide enough or the base of the tongue is raised, the medical staff will fix the tongue with a tongue depressor, take a sampling cotton swab in their right hand and brush the tonsils and posterior pharyngeal wall on both sides of the mouth repeatedly to collect mucosal epithelial cells.
5. Why not promote deep sputum collection of nucleic acids?
Phlegm comes from the infection focus of the lower respiratory tract, which generally needs to be coughed up hard. There is basically no deep sputum in the human body and it will not get sick. In addition, patients in COVID-19 usually have a dry cough, and it is difficult to obtain samples of deep expectoration. Saliva is the main component that most people spit out from their throats when they cough lightly. If the sample quality is poor, the probability of false negative of nucleic acid detection will be greatly increased.
6, suffering from pharyngitis, colds, etc. Will affect COVID-19 nucleic acid detection.
COVID-19 nucleic acid test is a specific test, which is a manifestation of COVID-19 infection, so colds, pharyngolaryngitis and so on will not affect the test results.