2.2 Specimen collection and processing
All bronchoscopies were performed by the same experienced bronchoscopist. Each patient was locally anesthetized with 2% lidocaine, then an ultrathin bronchoscope (BF-typ XP260F; Olympus: external diameter, 2.8 mm; channel diameter, 1.2 mm) was navigated to the target bronchus as far as possible using the VBN system (Direct Path 1.0). TBLB, BB and bronchoalveolar lavage (BAL) of peripheral lesions were performed in sequence in all subjects. On each patient, TBLB was performed at first, meanwhile ROSE were performed during the examination to determine whether the sample was sufficient for diagnosis. Then BB was performed using a protective needle brush and BALF specimens were obtained after brushing samples. The specimens obtained with TBLB and BAL were separately sent to the clinical microbiology laboratory for culture and sequencing company for mNGS, the TBLB specimens were also sent to the pathological laboratory for pathological examination. The protective needle tips were cut with sterile scissors and placed in a 2 ml sterile microcentrifuge tubes containing 1 ml of sterile saline and sent to the sequencing company for mNGS.