Setting: There has been a marked increase in notified cases of smear-negative pulmonary tuberculosis in Malawi since 1986. One reason for this may be related to the difficulties of getting adequate samples of expectorated sputum from patients. Sputum induction with nebulized hypertonic saline may be a simple way of obtaining a better specimen.
Objective: To examine the value of sputum induction for detecting cases of smear-positive tuberculosis.
Design: Sputum induction was performed on 82 adults presenting to the Queen Elizabeth Central Hospital, Blantyre, Malawi with clinically suspected pulmonary tuberculosis who were expectorated sputum smear-negative or unproductive of sputum. The induced sputum smear was examined for acid-fast bacilli and cultured for mycobacteria.
Results: Sputum was successfully induced from 73 of the 82 patients (26 previously smear-negative and 47 previously unproductive). The induced sputum was smear-positive in 18 patients (5 previously smear-negative and 13 unproductive). Cultures were positive for Mycobacterium tuberculosis in the 18 smear-positive patients and a further 12 that had been smear-negative. 94 cases of smear-positive pulmonary tuberculosis were notified during the study period. 18 (19%) were as a result of sputum induction.
Conclusion: Sputum induction is a useful technique for improving the case detection rate of smear-positive tuberculosis in Malawi.