Chest Computed Tomography Features of Nontuberculous Mycobacterial Pulmonary Disease Versus Asymptomatic Colonization: A Cross-sectional Cohort Study.

Background: Asymptomatic colonization by nontuberculous mycobacteria (NTM) found in sputum isolates are commonly encountered and clinicians lack a biomarker for prognosticating the risk of transition asymptomatic colonization to active clinical disease. Chest computed tomography (CT) imaging is commonly obtained in this patient population and may serve a role for this purpose.

Methods: We conducted a single-center, cross-sectional study of patients followed in the NTM clinic at our center between August 2019 and August 2020. All patients had a history of NTM isolated from their airways and were cohorted as either nontuberculous mycobacteria-pulmonary disease (NTM-PD) if they met ATS/IDSA guidelines for treatment or as nontuberculous mycobacteria-colonized (NTM-C) if they did not meet ATS/IDSA criteria for NTM treatment. Patients with a chest CT were included in the analysis and CT scans were assessed for features including bronchiectasis, nodules, and cavities. Bronchiectasis severity was calculated using the modified Reiff scoring system. Univariate analyses were conducted to compare patients with NTM-C and NTM-PD.

Results: Eighty-four patients were included in the analysis and 27 were classified as NTM-C and 57 as NTM-PD. NTM-PD patients had a greater median number of lung lobes affected by bronchiectatic airways (6 [1] NTM-PD vs. 5 [3] NTM-C P=0.005) and a greater frequency of cystic bronchiectasis (17.5% NTM-PD vs. 0% NTM-PD, P=0.016). Bronchiectasis severity was higher for NTM-PD patients (7 [9] NTM-PD vs. 5 [1.5] NTM-C, P<0.001).

Conclusions: Patients with NTM-PD have greater bronchiectatic airway involvement and the forms of bronchiectasis present are more severe compared with NTM-C patients. In addition, cavitation of lung parenchyma was a radiographic feature solely associated with NTM-PD. Features identified on chest CT may be useful as a prognostic biomarker for the risk of transition from NTM-C to NTM-PD.