Yield of computed tomography and bronchoscopy for the diagnosis of Mycobacterium avium complex pulmonary disease

Mycobacterium avium complex (MAC) pulmonary disease with nodules and bronchiectasis is increasing. But the usefulness of computed tomography (CT) and bronchoscopy for diagnosis and the significance of MAC isolation from respiratory secretions are still unclear. For a 4-yr period, we prospectively examined the role of bronchoscopy with bronchial washing and transbronchial lung biopsy in 26 patients who had clusters of small nodules in the periphery of the lung associated with ectatic changes of the draining bronchi on the CT scan. None of them was infected with human immunodeficiency virus. Thirteen of the 26 patients (50%) had cultures positive for MAC, six in the sputum and 13 in the bronchial washing. Epithelioid granuloma was demonstrated in eight of 13 patients with culture-positive MAC and in two of 13 patients in whom MAC was culture-negative. Rapidly growing mycobacteria were cultured in the two patients. Seven of the eight biopsy-positive patients received treatment and responded by sputum conversion and/or radiographic improvement. We found that the CT finding was a useful clue to suspect MAC pulmonary disease and that the bronchial washing was more sensitive than the routine expectorated sputum for MAC isolation. Demonstration of granuloma in more than half of the MAC-positive patients would suggest that MAC may have invaded the lung tissue rather than colonized in the airways.