Antigen detection test: how to collect pharyngeal specimen correctly - part 2

Throat swab is the most important sampling method for diagnosing COVID-19 infection. Correct sampling is the key to improve the accuracy of pharyngeal swab nucleic acid detection.

Pharyngeal division includes nasopharynx, oropharynx and laryngopharynx. The mucous membranes of the three are continuous and belong to the area of upper respiratory tract. The sampling path of nasopharyngeal swab and oropharyngeal swab is different. Oral sampling is oropharyngeal swab and nasal sampling is nasopharyngeal swab. If the nasopharynx swab is not collected deep in the nasopharynx cavity, the patient's nausea and lack of cooperation during the collection of oropharyngeal swab lead to insufficient sampling time, which may lead to the failure to collect samples containing virus, that is, it may cause "false negative".

Tips for nasopharyngeal swab collection

1. Preparation before sampling: give the sampling tube to the patient, let the patient take the tube, inform the patient that there may be discomfort during sampling, and inform the patient that the tube needs to be held vertically, so that the patient can concentrate on the tube, so as to reduce the discomfort caused by nasopharyngeal stimulation during sampling. Nasal swab patient has discomfort and inhales deeply

2. Posture during sampling: tilt the patient's head back 70 degrees to straighten the channel between nose and nasopharynx.

3. Standardize the sampling operation: "one insertion, two stops and three rotations" - measure the distance from the tip of the nose to the front of the ear, half of the insertion length, which is usually about 4cm for adults; Stay for 15-30 seconds to absorb part of the secretion of nasopharynx (depending on the patient's tolerance, the minimum stay time shall not be less than 3 seconds; rotate the nasopharynx swab around the joint and then take it out slowly.

4. Precautions: the sampler stands on the side of the patient and requires the patient to pull down the mask to expose only the nostrils. In case of sneezing reflex,

Patients can be covered with elbows or paper towels. The sampler is not directly in front of the patient, so the risk of exposure is quite low.

In clinical practice, many patients with hypertrophic turbinate and narrow nasal meatus can't use force rashly when the pharyngeal swab feels resistance. They can try to change one side of the nasal cavity or directly change to oropharyngeal swab collection. Those with nasal allergy symptoms are easy to induce sneezing. It is recommended to take oropharyngeal swab samples.