High-resolution CT of nontuberculous mycobacterium infection in adult CF patients: Diagnostic accuracy

Objectives: To determine the diagnostic accuracy of highresolution computed tomography (HRCT) for the detection of nontuberculous mycobacterium infection (NTM) in adult cystic fibrosis (CF) patients. Methods: Twenty-seven CF patients with sputum-cultureproven NTM (NTM+) underwent HRCT. An age, gender and spirometrically matched group of 27 CF patients without NTM (NTM-) was included as controls. Images were randomly and blindly analysed by two readers in consensus and scored using a modified Bhalla scoring system. Results: Significant differences were seen between NTM (+) and NTM (-) patients in the severity of the bronchiectasis subscore [45 % (1.8/4) vs. 35 % (1.4/4), P=0.029], collapse/ consolidation subscore [33 % (1.3/3 vs. 15 % (0.6/3)], treein- bud/centrilobular nodules subscore [43 % (1.7/3) vs. 25 % (1.0/3), P=0.002] and the total CT score [56 % (18.4/33) vs. 46 % (15.2/33), P=0.002]. Binary logistic regression revealed BMI, peribronchial thickening, collapse/ consolidation and tree-in-bud/centrilobular nodules to be predictors of NTM status (R2=0.43). Receiver-operator curve analysis of the regression model showed an area under the curve of 0.89, P<0.0001. Conclusion: In adults with CF, seven or more bronchopulmonary segments showing tree-in-bud/ centrilobular nodules on HRCT is highly suggestive of NTM colonisation. Key Points: • Lung function declines rapidly in cystic fibrosis patients with nontuberculous mycobacterium infection • High-resolution computed tomography can help identify nontuberculous mycobacterium in CF patients • Extensive collapse/consolidation and tree-in-bud/ centrilobular nodules are predictive of NTM infection • Multiple bronchopulmonary segments showing tree-inbud/ centrilobular nodules strongly suggest nontuberculous mycobacterium infection.

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