Comparison of induced versus expectorated sputum for diagnosis of pulmonary tuberculosis by acid-fast smear

Objective: To evaluate the sensitivity of induced versus expectorated sputum for the diagnosis of pulmonary tuberculosis by acid-fast smear. Methods: We performed a retrospective review of data on patients with cultures from respiratory secretions that were positive for Mycobacterium tuberculosis. We analyzed data on the 114 patients with positive cultures during a 4-year period in an urban tertiary care academic medical center. Results: Sputum samples had been obtained for 103 of the 114 patients with cultures positive for tuberculosis. Forty-four of the 114 patients were HIV seropositive. Overall 33 of 79 patients (42%) had positive acid-fast smears of expectorated sputum, and 6 of 24 (25%) had positive smears of induced sputum (p = 0.21). When data were analyzed for subgroups by HIV serostatus, there was no significant difference in the results. Estimated cost of sputum induction for 1 year was approximately $45,000. Conclusions: We found sputum induction to be costly, and induced sputum offered no advantage over routine expectorated sputum for the diagnosis of pulmonary tuberculosis.