Nasal swab to detect new crowns, why is it better than oral swab?
What is the difference between nasal swabs and oral swabs? 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, nasal swabs and oral swabs are only different sampling paths, transoral sampling is oropharyngeal swabs, transnasal sampling is nasal swabs.
However, because oral swabs are relatively simple to perform with an open mouth, they are more commonly used clinically, but the risk of exposure to the sampler is higher.
Why choose to conduct nasopharyngeal swab training instead of oropharyngeal swab training?
Dr. Faya Liang, deputy director, said that although oropharyngeal swabs are most commonly used for transoral sampling, this operation is also a high-risk operation, as the operator often needs to face the patient's mouth, and the patient is prone to irritating dry cough and vomiting during the collection process, exposing the collector to the virus-carrying aerosol.
Deputy Director Liang Faya said that nasal swabs have the following advantages over oral swabs.
1. It can be left 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 oral 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.
3. The exposure risk of the sampler is lower compared to oral 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.
What is the key to pharyngeal swab collection?
If a pharyngeal swab 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 and do not know the structure of the nasal cavity and nasopharynx are often unsure about the procedure of collecting nasopharyngeal swabs. For this reason, three deputy chief physicians, Liang Faya, Tian Peng and Cai Yuexin, conducted training in their respective wards and made a video of the nasopharyngeal swab sampling process for this purpose, which was placed in a WeChat group so that everyone could watch it repeatedly and master the key points.
"After 2 demonstrations in the 11th floor East Union Ward, where Dr. Tian Peng, the deputy chief physician, is located, the teammates from other hospitals quickly mastered this method, which shows that this 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.
