Nasopharyngeal swab have some advantages over oropharyngeal swab:

1. Nasopharyngeal swab can stay in the pharynx for a long time in order to obtain more samples, which is why the positive rate of nasopharyngeal swab is higher than that of oropharyngeal swab.
2. the exposure risk of the Nasopharyngeal swab sampler is lower than that of the oropharyngeal swab, because we can stand behind the patient when sampling, and require the patient to pull down the mask to expose only the nostrils and cover the mouth, and there is no need to look directly at the patient's oral cavity. And there is almost no pharyngeal reflex with Nasopharyngeal swab, a few patients may have sneeze reflex after sampling, and the patient can be covered with elbows or paper towels, and because the sampler is not directly in front of the patient. The exposurerisk of Nasopharyngeal swab is relatively lower, reducing the psychological pressure of the samplers.

The disadvantage of the Nasopharyngeal swab is that the patients with oral and pharyngeal swabs have greater psychological fear, and the samplers have more professional training.

Whether it is to collect nasopharyngeal swab or oropharyngeal swab, the depth of collection and the duration of contact with the mucosa are the key points. If the nasopharyngeal swab is not collected in the depths of the nasopharyngeal cavity, the patient has a strong vomiting reaction when collecting the oropharyngeal swab, which leads to insufficient sampling time. At this time, most of the cells that may be collected are virus-free cells, which may cause "false negative". This may also be one of the reasons why patients with negative nucleic acid test appear nucleic acid positive again during reexamination. In a chinese study, NPA and OPS methods were compared, SARS, MERS and H1N1 respiratory sampling literatures were reviewed, and it was concluded that among all upper respiratory tract sampling methods, Nasopharyngeal swab and oropharyngeal swab (NS+OPS) were the least harmful to medical staff.