Usefulness of Post-bronchoscopy Sputum Culture for Diagnosis of Nontuberculous Mycobacterial Pulmonary Disease

Background Bronchoscopy is recommended for patients with suspected nontuberculous mycobacterial pulmonary disease (NTM-PD) whose sputum culture results are consistently negative or from whom adequate sputum samples cannot be obtained. Post-bronchoscopy sputum (PBS) collection is recommended for patients with suspected tuberculosis who undergo bronchoscopy. However, it remains unclear whether PBS collection can increase the diagnostic yield of NTM-PD. Methods Patients with suspected NTM-PD who underwent diagnostic bronchoscopy from January 1, 2017 to June 30, 2020 at the Seoul National University Hospital were included in the study. They were divided into the sputum culture-negative and scanty sputum groups. The results of mycobacterial cultures from bronchial washing specimens and PBS were compared between these groups. Results In total, 141 patients were included in the study; there were 39 and 102 patients in the sputum culture-negative and scanty sputum groups, respectively. Nontuberculous mycobacteria were cultured from bronchial washing specimens collected from 38.3% (54/141) of all patients (30.7% [12/39] patients in the sputum culture-negative group and 41.2% [42/102] patients in the scanty sputum group; P = 0.345). Nontuberculous mycobacteria were exclusively cultured from PBS collected from 3.5% (5/141) of all patients (7.7% [3/39] patients in the sputum culture-negative group and 2.0% [2/102] patients in the scanty sputum group; P = 0.255). Conclusions Additional PBS collection improved diagnostic yield marginally in patients with suspected NTM-PD who undergo bronchoscopy.