What is the difference between a throat swab and a nasopharyngeal swab which is more accurate

Wuhan has launched a full-staff nucleic acid test for screening. At present, many communities have begun to conduct statistics on related personnel and work. However, during the test, everyone also found that some use throat swab testing, and some use nasal swab testing. , So what is the difference between the two, which one is more accurate, and what issues should everyone pay attention to when conducting nucleic acid testing.

What is the difference between a throat swab and a nasopharyngeal swab

The pharynx includes nasopharynx, oropharynx, and laryngopharyngeal. The mucous membranes of the three are continuous and belong to the upper respiratory tract. Nasopharyngeal swabs and oropharyngeal swabs only have different sampling paths. Oral sampling is oropharynx Swab, nasal sampling is nasopharyngeal swab. However, because the oropharyngeal swab can be operated by opening the mouth, it is relatively simple, so it is more commonly used clinically, but the risk of exposure of the sampler is higher.

The new coronavirus pneumonia nucleic acid test can take the patient's nasopharyngeal swabs, sputum and other lower respiratory secretions, blood, feces and other samples for testing. For the new coronavirus nucleic acid, if the nucleic acid of the sample is positive, the virus infection can be confirmed.

The new coronavirus infection mainly affects bronchial epithelial cells and alveolar epithelial cells. Lower respiratory tract specimens, such as sputum and airway extracts, should be used as much as possible to more accurately reflect the virus infection.

Advantages of nasal swabs

1. It can stay in the pharynx for a longer period of time in order to obtain more sufficient samples. This is also the reason why the positive rate is higher than that of oropharyngeal swabs reported in the literature.

2. The patient is well tolerated, and can basically take samples without anesthesia after proficient operation, but the surface anesthesia and contraction of the nasal mucosa can be performed at the beginning.

3. The exposure risk of the sampler is lower than that of the oropharyngeal swab, because when sampling, we can stand behind the patient and ask the patient to pull down the mask to expose only the nostrils and cover the oral cavity without looking directly at the patient’s oral cavity. Moreover, there is basically no pharyngeal reflex. A few patients may have sneeze reflex after sampling. The patient can be covered by elbows or tissues. Because the sampler is not in front of the patient, the exposure risk is quite lower, so the psychological pressure of the sampler will not be so great. .

Sampling considerations

Whether collecting nasopharyngeal swabs or oropharyngeal swabs, the depth of collection is the key. The collected nasopharyngeal swabs are not collected deep into the nasal cavity. Most of the cells collected are virus-free cells, which may cause "False negative".

Sampling process

1. The sampler holds the swab with the right hand (plastic swab with polypropylene fiber head), and presses the top of the subject's head with the left hand to fix it.

2. Make the swab with the tip slightly bent down from the front nostril and go deep along the bottom of the lower nasal passage. {Because the nasal passage is curved, the movement should be gentle and slow. Do not use excessive force to avoid traumatic bleeding} .

3. When the tip of the swab reaches the back wall of the nasopharyngeal cavity (with a feeling of touching the wall), leave the swab for a while (about 3 seconds), and then gently rotate it one week to slowly take out the swab.

4. You can take another plastic rod swab with a polypropylene fiber head to collect the other nostril in the same way, immerse the above 2 swabs into the same tube containing 3ml virus sampling solution, discard the tail, and tighten the tube cap .

5. After being packaged according to biosafety requirements, it should be transported to CDC laboratories at all levels for viral nucleic acid testing as soon as possible.

Inspection notes

To avoid vomiting, please refrain from eating 2 hours before sampling;

To avoid affecting the test results, please refrain from smoking, drinking and chewing gum 30 minutes before sampling;

In order to reduce the risk of cross-infection in the hospital, all those who come to the hospital for testing need to wear a mask and prepare a spare mask;

All personnel waiting for inspection must keep a distance of more than 1 meter to avoid talking;

It is necessary to bring the patient's ID card and receipt when sampling and taking the report.