Pharyngeal swab sampling only requires that the swab head be inserted into the patient's pharynx and the tonsils and throat wall be wiped, in other words, the sampling is done by scraping at the throat.
The lower respiratory tract is generally sampled by alveolar lavage: Bronchoalveolar lavage procedure.
(1) First, inject 1-2 ml of 2% lidocaine through a thin silicone tube into the lung segment to be lavaged through the biopsy hole to provide local anesthesia.
(2) Then wedge the tip of the cilioscope closely into the opening of the segment or subsegment of the bronchus, and then rapidly inject sterile saline at 37°C through the biopsy hole through a silicone tube, 20-50 ml each time, 100-250 ml in total, usually not more than 300 ml.
(3) Immediately recover the lavage fluid with 50-100 mmHg negative pressure suction, usually with a recovery rate of 40%-60% (
(4) Immediately filter the recovered fluid through a double layer of sterile gauze to remove the mucus and record the total amount.
(5) Place in a silicone plastic bottle or silicone coated sterilized glass container (to reduce cell adhesion), place in a thermos containing ice, and send immediately to the laboratory for examination. Compared to pharyngeal swab sampling, alveolar lavage sampling is significantly more cumbersome, requiring anesthesia and saline lavage of the patient, and it is difficult to test alveolar lavage in every case with the current form of strained medical resources.
So now for suspected patients, additional medical testing may be needed to supplement sampling of the lower respiratory tract and nucleic acid testing in patients with typical symptoms of neoconjunctivitis but recessive pharyngeal swab nucleic acid testing to make a secondary diagnosis of the patient and rule out potential false negatives.
There is also another possibility that the patient showed positive nucleic acid testing for influenza A on admission to the hospital. It is possible that the patient was unfortunately exposed to a source of neo-coronavirus infection after being admitted to the hospital with influenza A infection, which led to his re-infection with neo-coronavirus and was diagnosed as a patient with neo-coronavirus pneumonia on subsequent alveolar lavage fluid testing.
Reference.
Chinese Society of Medical Sciences, Respiratory Diseases Branch. Technical specifications for cytological testing of bronchoalveolar lavage fluid (draft) [J]. Chinese Journal of Tuberculosis and Respiratory Diseases, 2002, 25(7):390-391.
Author: 123456
Link: https://www.zhihu.com/question/370433264/answer/1004980847
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