Computed tomographic diagnosis of Mycobacterium avium-intracellulare complex in patients with bronchiectasis

We tested the hypothesis that bronchiectasis and multiple small lung nodules seen on chest computed tomography (CT) are indicative of Mycobacterium avium-intracellulare complex (MAC) infection or colonization by reviewing CT scans and histories of 100 outpatients with CT diagnosis of bronchiectasis. Of the 24 patients with multiple pulmonary nodules, 19 had lung nodules and bronchiectasis in the same lobe. Mycobacterial cultures were performed on 63 of the 100 patients, including 15 of the 24 patients with lung nodules and 48 of the 76 patients with no lung nodules. Of the 15 patients with lung nodules, 8 (53 percent) had cultures positive for MAC, as did 2 of the 48 (4 percent) patients with no CT evidence of lung nodules. The number of cultures positive for fungi was approximately the same in both groups. In our outpatient population, CT prediction of cultures positive for MAC in bronchiectatic patients with multiple small lung nodules has a sensitivity of 80 percent, a specificity of 87 percent, and an accuracy of 86 percent.