What is a pharyngeal swab?

Five things you need to know about the new coronavirus nucleic acid test.

With the back-and-forth of the outbreak, nucleic acid test reports and Code Green have become essential passes. Nucleic acid testing and pharyngeal swabs seem to have become the medical devices we hear the most about throughout the year. We all know where to go for a nucleic acid test, too, but what actually happens during a nucleic test? What does it mean if the test comes back negative? If you haven't had a nucleic acid test yet, you might want to read this article first. This article will popularize five things about nucleic acid testing.

1. What is a pharyngeal swab? How is it collected? What should I pay attention to?

Pharyngeal swabs are divided into nasopharyngeal swabs and oropharyngeal swabs.

(1) Nasopharyngeal swab is a sampling tool to extract epithelial cells and secretions from the nasopharynx. The sampling method is to use a sterilized nasal swab to penetrate deep into the nasal cavity and reach the nasopharynx to extract secretions and nasopharyngeal epithelial cells by rotating or wiping, etc. The nasal swab with secretions stuck to it is then placed inside the virus sampling tube for pathogenic testing.

Note: Our body can be unaccustomed to this action. On the one hand, it activates the lacrimal reflex, which means that if done correctly it will stimulate tearing. Since the swab also touches the back of the throat, it may also trigger the vomiting reflex.

(2) The oropharyngeal swab, a sampling tool for extracting mucosal cells and secretions from the oropharynx. The sampling method is to use an object such as a sterilized pharyngeal swab to penetrate deep into the pharynx, through the root of the tongue to the posterior pharyngeal wall, tonsillar crypt, and lateral wall, repeatedly wiping left and right 2 to 3 times, and gently removing the swab. The swab stained with mucosal cells and secretions was then placed into a virus sampling tube. Send for pathogenetic testing.

Note: When sampling oropharyngeal swabs, the patient should open the mouth as much as possible and the medical staff should observe the pharynx repeatedly before taking the sample. To avoid affecting the test results, pharyngeal swab sampling for bacterial culture should be done before taking antibiotic medications if possible. Oropharyngeal swabs are best taken before eating, in addition to rinsing the mouth before sampling, and avoiding touching the tongue, pendulous body, oral mucosa and saliva when taking samples and removing swabs.

2. Are there other new crown tests?

Saliva is another specimen type that is being explored and the preliminary data does look promising. But we are still waiting for larger studies to confirm these initial findings. In addition to nucleic acid testing, which can detect viral genetic material, antigen testing is also available, which can detect viral proteins that stimulate antibody production or the immune system's response to an invader. While antigen tests are faster, they are also much more sensitive than nucleic acid tests. Therefore, even if a positive antigen test is beneficial, a negative result is more likely to be confirmed by a more sensitive nucleic test.

3. What should I do if I need to be tested for a new crown?

At present, basically all provincial tertiary hospitals have the ability to do nucleic acid testing, and there are also designated hospitals in each city that can do it. You can make an appointment through the hospital's official website. The nucleic acid test is usually performed in the morning and the results are now available the next day.

4. Is it possible for me to get a false negative test result?

This is a common question and it is important to point out that patients who are in the early stages of infection and are asymptomatic may have a negative test result. A repeat test on that individual is likely to be positive because the amount of virus in their body has increased to a detectable level. If your physician believes the index of suspicion for the new coronavirus is high, they may repeat the test to confirm the initial results.

5. Does a negative nucleic acid test rule out New Coronavirus pneumonia?

A negative nucleic acid test does not completely rule out neo-coronavirus infection. The neo-coronavirus mainly attacks the mucous membrane of the lungs and relatively little of the upper respiratory tract. Therefore, it has been found that in some patients, the nucleic acid test of the pharyngeal swab has been negative for one, two or even three times, while it was found positive only on the fourth time or on sputum examination. It is important to be highly vigilant based on the epidemiological history, if indeed there is a history of close contact with neocoronavirus pneumonia, even if it is negative for 1 or 2 times. This can be done repeatedly and again, or sputum specimens can be retained for nucleic acid testing. Therefore, if the result is negative, it is necessary to test again and measure several times negative before the risk can be excluded.