7. Bronchoalveolar lavage
The earliest identification of the SARS-CoV-2 genome was performed via bronchoalveolar lavage (BAL) samples in the Wuhan Institute of Virology.20 Bronchoalveolar lavage (BAL) is a form of the lower respiratory system sampling in which a bronchoscope is introduced into the trachea and bronchi, and a calculated amount of fluid is introduced and then collected for examination. Since December 2019, studies from China and Europe on the use of BAL specimens for SARS-CoV-2 viral detection have been published.21-23Accumulating evidence suggest that BAL may be useful in viral detection in cases of false-negative NPS and/or OPS.24 In a study of 4880 suspect COVID-19 patients in Wuhan, Liu et al found that BAL exhibited the highest positive rate for SARS-CoV-2 detection and reported that the NS and OPS showed a poor combined positive rate of 38.25% while collected sputum exhibited a 49.12% positive rate. The case definition of a suspect COVID-19 patient in the study was based on the following: 1) typical respiratory infection symptoms such as fever, cough and hard (difficult) breathing , or 2) close contact with a SARS-CoV-2 patient.25