Nasopharyngeal swab have some advantages over oropharyngeal swab: Nasopharyngeal swab can stay in the pharynx for a long time in order to obtain more samples, which is why the positive rate of nasopharyngeal swab is higher than that of oropharyngeal swab. the exposure risk of the Nasopharyngeal swab sampler is lower than that of the oropharyngeal swab, because we can stand behind the patient when sampling, and require the patient to pull down the mask to expose only the nostrils and cover the mouth, and there is no need to look directly at the patient's oral cavity. And there is almost no pharyngeal reflex with Nasopharyngeal swab, a few patients may have sneeze reflex after sampling, and the patient can be covered with elbows or paper towels, and because the sampler is not directly in front of the patient. The exposurerisk of Nasopharyngeal swab is relatively lower, reducing the psychological pressure of the samplers. The disadvantage of the Nasopharyngeal swab is that the patients with oral and pharyngeal swabs have greater psychological fear, and the samplers have more professional training. Whether it is to collect nasopharyngeal swab or oropharyngeal swab, the depth of collection and the duration of contact with the mucosa are the key points. If the nasopharyngeal swab is not collected in the depths of the nasopharyngeal cavity, the patient has a strong vomiting reaction when collecting the oropharyngeal swab, which leads to insufficient sampling time. At this time, most of the cells that may be collected are virus-free cells, which may cause "false negative". This may also be one of the reasons why patients with negative nucleic acid test appear nucleic acid positive again during reexamination. In a chinese study, NPA and OPS methods were compared, SARS, MERS and H1N1 respiratory sampling literatures were reviewed, and it was concluded that among all upper respiratory tract sampling methods, Nasopharyngeal swab and oropharyngeal swab (NS+OPS) were the least harmful to medical staff.

Pharynx: Deep in the nose and mouth, it can be divided into: nasopharynx, oropharynx, and laryngopharynx. When doing nucleic acid, the most commonly sampled areas are the nasopharynx and oropharynx. The reason is that when the virus enters the respiratory tract, very little virus remains in the outer locations, and most of it accumulates in the nasopharynx and oropharynx, which are inside the respiratory tract. Why use anterior nasal swab antigenself-test sampling? Anterior nasal swab is widely use in antigen self-test, because the length of anterior nasal swab is suitable for selftest, besides, although there are few viruses in the nasal cavity, there are more secretions, while in the oral cavity exhalation is large, swallowing is frequent, leaving less virus, there may be false negative test results appear. Therefore, anterior nasal swabs are more commonly used than anterior pharyngeal swabs for antigen self-testing In the case of patients with chronic or allergic rhinitis, it is recommended to blow the nose before anterior nasal swab sampling, but do not wash the nose with saline to avoid affecting the concentration of virus in the nasal cavity, resulting in affecting the sensitivity of the test. In addition, collection of oropharyngeal swab instead of anterior nasal swabis recommended if there is a history and risk factors associated with. Patients with severe allergic rhinitis. Those with malformations in the nasal cavity, such as curvature of the nasal septum. Those with recent symptoms of nasal bleeding. Those who have undergone nasal surgery for not more than 3 months. Those with blood disorders or long-term use of anticoagulant drugs.

The quality of the Viral Transport Tube is not only the "visible" performance indicators, but also the "invisible" performance indicators: 1. "Visible" performance indicators: Directly observed quality indicators such as Viral Transport Tube material, process level, sealing performance, and filling accuracy. 2. "Invisible" performance indicators: include the preservation effect of viral nucleic acid, the preservation effect of the minimum detection limit, microbial indicators, virus inactivation efficiency, etc. These indicators are the key to determining the detection of viral nucleic acid. Preservation effect of viral nucleic acid of Viral Transport Medium: The main function of Viral Transport Medium is to maintain the integrity of viral RNA nucleic acid and inhibit nucleic acid cleavage. Temperature, transportation conditions, and storage days all have an impact on the integrity of RNA. The better the RNA protection, the more accurate the nucleic acid detection of the virus. Virus inactivation efficiency of Viral Transport Medium: The inactivated Viral Transport Medium can improve the safety during sample collection and transportation. Minimum detection limit preservation effect: of Viral Transport Medium: Ensure that samples with low viral loads are detected and false negative test results do not occur. Microbiological indicators of Viral Transport Medium: The presence of microorganisms will accelerate the degradation of viral RNA and affect the sensitivity of nucleic acid detection. The Viral Transport Medium in the Viral Transport Tube is added with the color indicator phenol red. Under normal circumstances, the liquid should be alkaline and the color is purple. Once the microorganisms in the Viral Transport Tube are not up to standard, their reproduction will cause the pH value of the liquid to drop, and the preservation solution will turn yellow.