Changing patterns of mycobacterial disease at a teaching community hospital.

OBJECTIVES

To evaluate trends in the occurrence and diagnosis of mycobacterial disease.

DESIGN

Prospective surveillance study using a central tuberculosis registry at a 611-bed teaching community hospital.

RESULTS

Data pertaining to 715 patients were entered into the registry between 1976 and 1991 on the basis of positive smears or cultures for acid-fast bacilli (AFB). Over time, the ratio of isolates of Mycobacterium tuberculosis to isolates of nontuberculous mycobacteria reversed (from 3.2 to 1 between 1976 and 1981 to 1 to 1.6 between 1986 and 1991). The sensitivity of the sputum AFB smear for diagnosis of pulmonary tuberculosis increased (from 0.73 to 0.96), but the positive predictive value of the sputum AFB smear declined (from 0.72 to 0.59). The acquired immunodeficiency syndrome epidemic accounted for these changes only to a small extent.

CONCLUSIONS

The increasing occurrence of non-tuberculous mycobacterial disease and the declining positive predictive value of the sputum AFB smear at this hospital imply that respiratory isolation and antituberculous therapy will be used inappropriately for many patients. The development and use of newer tests for early isolation and specific identification of M tuberculosis should be accelerated.