Recently, in order to further improve the efficiency of pharyngeal swab collection and reduce the exposure of collectors, three associate chief physicians, Dr. Liang Faya, Dr. Tian Peng and Dr. Cai Yuexin, and two nurses, Dr. Chen Wen and Dr. Lu Zhiyin, from the Department of Otorhinolaryngology of the second batch of medical team supporting the prevention and control of the epidemic in Hubei of Sun Yat-Sen Memorial Hospital of Sun Yat-sen University, conducted training and sampling of nasopharyngeal swabs in the wards on the 7th floor east, 11th floor east and 14th floor west of the West Campus of the Union Hospital of Huazhong University of Science and Technology, respectively. The training and sampling of nasopharyngeal swabs was carried out.
The nucleic acid test results of the new coronavirus are an important reference for the diagnosis and efficacy evaluation of novel coronavirus pneumonia. Nucleic acid test screening specimens mostly come from deep cough sputum or pharyngeal swabs, which are divided into nasopharyngeal swabs and oropharyngeal swabs.
So, what is the difference between the two? Cai Yuexin, deputy chief physician, introduced that the pharyngeal partition includes nasopharynx, oropharynx, laryngopharynx, the mucosa of the three is continuous, all belong to the area of the upper respiratory tract, nasopharyngeal swabs and oropharyngeal swabs are just different sampling paths, through the mouth is the oropharyngeal swab, through the nose for nasopharyngeal swabs. However, oropharyngeal swabs are more commonly used clinically because they can be performed with the mouth open and are relatively simple, but the risk of exposure to the sampler is higher.
Why is nasopharyngeal swab training chosen over oropharyngeal swab training? Dr. Liang Faya, deputy chief physician, said that although oropharyngeal swabs are most commonly used for transoral sampling, this operation is also a high-risk operation, the operator often needs to face the patient's mouth, and the patient is prone to irritating dry cough, vomiting and other symptoms during the collection process, exposing the collector to the aerosol with the virus.
Dr. Liang Faya, deputy chief physician, said that nasopharyngeal swabs have the following advantages over oropharyngeal swabs.
1. It can stay in the pharynx for a longer period of time to obtain a more adequate amount of specimen, which is the reason why its positive rate is reported in the literature to be higher than that of oropharyngeal swabs.
2. It is well tolerated by patients and can basically be sampled without anesthesia after skilled operation, but surface anesthesia and contraction of the nasal mucosa can be performed first when first learning.
The exposure risk of the sampler is lower compared to oropharyngeal swabs because the sampler can stand behind the patient's side during sampling, and the patient is required to pull down the mask to reveal only the nostrils and cover the oral cavity without looking directly into the patient's mouth, and there is basically no gag reflex. The risk of exposure is much lower because the sampler is not directly in front of the patient, so the psychological pressure on the sampler is not as great.
If the pharyngeal swab nucleic acid test specimen is not collected properly, it may result in a "false negative" result, which may delay the patient's treatment. So, what is the key to pharyngeal swab nucleic acid test specimen collection? Dr. Tian Peng, deputy chief physician, said that whether it is a nasopharyngeal swab or an oropharyngeal swab, the depth of collection and the length of contact with the mucosa are key.
If the nasopharyngeal swab is not collected deep into the nasopharyngeal cavity, or if the patient vomits during the collection of the oropharyngeal swab, resulting in insufficient sampling time, the majority of cells collected may be cells that do not contain the virus, which may result in a "false negative". This may also be one of the reasons why patients with multiple negative nucleic acid tests have been reported to have a positive nucleic acid test when retested.
Physicians and nurses who do not specialize in otolaryngology are not familiar with the structure of the nasal cavity and nasopharynx and are often unsure about the procedure of collecting nasopharyngeal swabs. For this reason, three deputy chief physicians, Liang Faya, Tian Peng and Cai Yuexin, respectively, conducted training in their wards and made a video of the nasopharyngeal swab sampling process for this purpose, which was placed inside the WeChat group so that everyone could watch it repeatedly and master the key points.
"After 2 demonstrations in the 11th floor east joint ward, where deputy chief physician Tian Peng and I are located, teammates from other hospitals quickly mastered the method, indicating that the method is not difficult." Liang Faya, deputy chief physician, said that a small number of patients may have a little nasal bleeding after sampling, generally can stop on their own, if necessary, can be used with epinephrine swabs slightly shrink the bleeding site to stop bleeding.
