The role of induced sputum in the diagnosis of pulmonary tuberculosis

Background: Microbiological confirmation of pulmonary tuberculosis (TB) is of paramount importance in the era of immunocompromised host and emergence of multi-drug resistance. Objectives: To assess the value of sputum induction (SI) with hypertonic saline nebulization as a diagnostic tool in patients with suspected pulmonary TB who have no/inadequate sputum or have a sputum smear negative for acid fast bacillus (AFB). Materials and Methods: One hundred patients with clinical and radiological evidence of pulmonary TB with no/inadequate sputum or smear negative with spontaneous sputum were studied. Sputum was induced with 20 mL of 3% hypertonic saline solution delivered through ultrasonic nebulizer. The specimens were subjected to Ziehl Neelsen staining and were examined under oil immersion lens for the presence of AFB. The specimens were also subjected to mycobacterial culture in BACTEC 460 TB system. Results: Ninety five patients could produce adequate sputum after SI. Sputum from thirty two patients were found to be positive both in smear and culture while sputum from another three patients were smear negative, but culture positive. Conclusion: SI is a safe, cheap and non-invasive procedure and provides significant yield in the diagnosis of pulmonary TB; thus, increasing the case detection rate of smear positive pulmonary TB.