Comparison of sputum induction with fiber-optic bronchoscopy in the diagnosis of tuberculosis

Abstract

Microbiologic confirmation of pulmonary tuberculosis among patients whose sputum smear is negative is increasingly important because of greater incidence among immunocompromised hosts and emergence of drug-resistant strains. We prospectively compared sputum induction to fiber-optic bronchoscopy in the diagnosis of such patients. Consecutive patients referred for investigation of possible active pulmonary tuberculosis underwent sputum induction with hypertonic saline delivered by an ultrasonic nebulizer between 2 and 48 h before transnasal fiber-optic bronchoscopy. All specimens were examined for acid-fast bacilli with fluorescent microscopy and cultured for mycobacteria. Clinical information was abstracted from patient records, and X-rays were reviewed by two blinded readers. Among 101 participants, sputum induction was well-tolerated without complications and provided adequate samples in 93. Sensitivity of direct acid-fast bacilli smear of specimens from both techniques was low. Sensitivity and negative predictive value of culture from bronchoscopy specimens was 73% and 91% compared with 87% and 96%, respectively, for sputum induction when a specimen was obtained. Direct costs for bronchoscopy totaled Canadian $187.60 compared with Canadian $22.22 for sputum induction. Sputum induction was well-tolerated, low-cost, and provided the same, if not better, diagnostic yield compared with bronchoscopy in the diagnosis of smear-negative pulmonary tuberculosis.