Abstract: Abstract: Objective To evaluate the diagnostic yield and safety of transbronchial lung biopsy (TBLB) under virtual bronchoscopic navigation (Direct Path), endobronchial ultrasonography with a guide sheath (GS) and rapid on-site evaluation using an ultrathin bronchoscopy (UNRE) for bacterial infection located in the peripheral third of the lung field. Methods Ninety-seven patients with bacterial infection, which located in the peripheral third of the lung field on CT images, were ran⁃ domly assigned to UNRE (n=49) or non-UNRE (NUNRE, n=48) groups, who were treated in General Hospital of Tianjin Medical University between April 1, 2014 and March 31, 2015. The TBLB guided by UNRE was performed in two groups. The diagnostic yield, safety and complication rate were compared between two groups. Moreover, the differences of autofluo⁃ rescence intensity of alveolar macrophage in alveolar lavage fluid were compared between two groups of patients. Results The diagnostic yield was significantly higher in UNRE group than that of NUNRE group (81.6% vs 56.2%, χ2 =7.313, P < 0.01). The diagnostic yield was higher in UNRE group with bronchus sign compared to that of NUNRE. All patients had a mild bleeding at the time of biopsy. There were no hemoptysis, pneumothorax or other serious complications. The autofluores⁃ cence intensity of alveolar macrophage was different in different levels of infection in patients. Conclusion The procedure of UNRE has higher diagnostic rate and fewer complications. The careful selection of suitable cases can further improve the diagnostic accuracy. The autofluorescence intensity of alveolar macrophage in alveolar lavage fluid indicates the severity of infection in patients.

Key words: Key words: ultrathin bronchoscopy, navigational bronchoscopy, endobronchial ultrasonography with guide sheath, rap? id on site evaluation, pulmonary infection, peripheral pulmonary lesion, autofluorescence, UNRE