HIGH PREDICTIVE VALUE OF THE ACID-FAST SMEAR FOR MYCOBACTERIUM-TUBERCULOSIS DESPITE THE HIGH PREVALENCE OF MYCOBACTERIUM-AVIUM COMPLEX IN RESPIRATORY SPECIMENS

The value of the smear for acid-fast bacilli in predicting pulmonary t uberculosis is unclear in a setting where there is a high prevalence o f Mycobacterium avium complex in respiratory specimens. To evaluate th e impact of high prevalence of M. avium complex on the predictive valu e of the acid-fast bacilli smear for tuberculosis, we reviewed finding s on smears and results of cultures over a 3-year period at a hospital where M. avium complex is the predominant mycobacterial isolate. In t his setting, the predictive value of the acid-fast bacilli smear for M ycobacterium tuberculosis was 92% for expectorated sputum specimens, 7 1% for induced sputum specimens, and 71% for bronchoalveolar lavage sp ecimens. When multiple specimens collected from the same patient were excluded from the data base, the predictive values were 87%, 70%, and 71%, respectively. Smears of sputum samples were positive at the same rate for patients with tuberculosis who had AIDS and for patients with tuberculosis who have not have AIDS.