2.1 Patient selection
All subjects gave written informed consent. Combining VBN, ultrathin bronchoscope, TBLB + ROSE + mNGS for the diagnosis infective PPLs is our routine process, and this is a retrospective study, therefore, no formal ethical approval was needed. We retrospectively enrolled consecutive patients who were clinically and radiologically suspected of having infectious PPLs and underwent ultrathin bronchoscopy assisted by the VBN system and mNGS for the diagnosis of PPLs in our hospital between July 2018 and July 2019. Patients who did not have TBLB, BB and BALF samples at the same time for mNGS were excluded.