Why do we use nucleic acid testing? How to choose between 3 types of swabs?

Since the outbreak of new coronavirus pneumonia, we have started to conduct accounting tests on a large scale in order to screen out positive patients as soon as possible.

There are two main types of technical methods researched regarding the detection of the new coronavirus: one is antibody for detection, and the other is a nucleic acid test. Antibody detection systems are mainly designed to use blood draws,Rapid antigen nasal swab and nucleic acid testing relies mainly on swabs, such as pharyngeal swabs, nasal swabs, and anal swabs. Antibody testing is designed to improve the observation of whether the antibody titer in the patient's body is increased, but this has little impact on the significance of the early functional test results in China; nucleic acid testing is mostly done with a pharyngeal swab, which has a higher specificity and sensitivity than that of the swabs.

Three types of swabs, each with its own characteristics

1. Pharyngeal swab: When sampling, the patient rinses his/her mouth with water, then opens his/her mouth and makes an "ah" sound, using a tongue depressor if necessary. The doctor uses a sterile cotton swab to gently and quickly wipe the lateral and posterior pharyngeal wall several times, which is the most commonly used method in clinical practice.

2. Nasal swab:For sampling, the swab is inserted into the nostril in a direction perpendicular to the nose (face) until the fingers are close to the nose, allowing the swab to remain in the nose for 15-30 seconds and then gently rotated 3 times.

3. Anal Swab: Insert the sampling swab 2-3 cm into the anus to take a sample, or use the swab to take a sample around the anal folds. The anal swab test is a new coronavirus test that has recently been introduced and was previously used mainly to screen for parasitic infections. If the usual diet is unhygienic, intestinal parasites can lay eggs and pass them in the feces, and it is then possible to detect the parasites using an anal swab.

It is worth mentioning that there are reports referring to the special case of a few discharged patients who had two negative nucleic acid amplification tests on throat swabs but positive anal swabs, it is recommended that anal swab testing may improve the detection rate of patients with 2019 Coronavirus Disease infections to some extent.

For anal swabbing, many people want to know under what circumstances it is used. In this regard, infectious disease experts say that there is a possibility of fecal-oral transmission of new coronavirus pneumonia. For example, patients with intestinal symptoms can have both anal swabs and pharyngeal swabs positive for new coronavirus pneumonia nucleic acid; in a few cases, after the pharyngeal swabs and nasal swabs turn negative for nucleic acid, the anal swab test is still positive. It is necessary to increase the anal swab.

Nucleic acid for testing system requires full cooperation of the subject

Nucleic acid sampling before 1.2 hours to avoid eating, half an hour to prohibit smoking, drinking alcohol, chewing gum;

2. The sampling process will be irritating dry cough, nausea, vomiting and other symptoms, try to relax and breathe deeply during the test.

3. Only when sampling can you remove a mask, please put it on immediately after the sampling process;

4. Due to individual differences, tolerance and past medical history, bleeding, infection, cardiovascular and cerebrovascular accidents and other rare complications and adverse consequences;

5. if you have previously suffered from blood diseases, throat diseases, taking anticoagulants and other related risk factors, you need to inform the healthcare personnel before sampling;

6. to leave the collection station immediately after collection to avoid spitting and vomiting around the collection station.

coronavirus detection Nasal swab Pharyngeal swab

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