In nucleic acid detection, what are the main types of samples collected at present, and what are their advantages and disadvantages?
On the afternoon of April 15, the Information Office of the Provincial Government held the 26th press conference on epidemic prevention and control in Shandong Province in 2022 to introduce the situation of epidemic prevention and control in COVID-19. Ding Shujun, deputy director of the Institute of Infectious Diseases Prevention and Control of the Provincial Center for Disease Control and Prevention, attended the conference and answered questions from reporters.
Population Health News reporter:
In nucleic acid detection, what are the main types of samples collected at present, and what are their advantages and disadvantages?
Ding Shujun: After the diagnosis of COVID-19, various samples can be collected for laboratory testing. Samples of upper respiratory tract can be collected, including nasopharyngeal swabs and throat swabs. You can also collect lower respiratory tract specimens, including deep expectoration, alveolar lavage fluid, bronchial lavage fluid, respiratory aspirate, etc. You can also collect stool samples/anal swabs, blood samples, serum samples, urine samples, etc.
At present, nasopharyngeal swab, oropharyngeal swab and sputum are commonly used in nucleic acid detection, each of which has its own advantages and disadvantages. The pharynx, located in the deep part of the nose and mouth, is divided into three parts: nasopharynx, oropharynx and laryngopharynx from outside to inside. Nasopharyngeal swab collection is what we often call "nose poking". It is to insert the sampling tool into the nasal cavity to collect nasopharyngeal specimens. The detection rate and accuracy will be higher, but the operation is more complicated and more difficult. Some people are not easy to adapt and their acceptance is slightly lower. The collection of oropharyngeal swabs is what we often call "stabbing the throat". By collecting oropharyngeal samples through the mouth, the sampler can see the position of the pharynx to be sampled, but it is irritating to the oropharyngeal mucosa when sampling, which may lead to cough, nausea and even vomiting. COVID-19 nucleic acid can also be detected by collecting sputum samples, especially deep sputum samples, and the positive detection rate is relatively high. However, the deep expectoration sample is not a saliva sample, and if no qualified deep expectoration sample is collected, false negative results may appear. Compared with nasopharyngeal swab and sputum specimen, oropharyngeal swab is faster, simpler and easier to operate, and the detection rate can meet the requirements. Usually, for low-risk people, it is enough to collect throat swabs for testing. For some high-risk groups, such as asymptomatic infected persons, immigrants and close contacts, in order to collect samples with high viral load and improve the positive detection rate, nasopharyngeal swabs should be collected for nucleic acid detection during isolated observation.
In large-scale population nucleic acid screening, throat swab samples are highly efficient, easy to be accepted by people, easy to organize and carry out, which can quickly screen out suspected positive people and take isolation control measures quickly, which is helpful for rapid disposal and effective control of the epidemic situation.