Induced sputum versus bronchial washings in the diagnosis of sputum negative pulmonary tuberculosis

INTRODUCTION: Tuberculosis (TB) is one of the most important public health problems worldwide. Detecting patients with active pulmonary TB (PT) is an important component of TB control programs. However, at times in patients even with a compatible clinical picture, sputum smears do not reveal acid-fast bacilli (AFB) and smear-negative PT remains a common problem. This study compares the results of induced sputum (IS) and bronchial washings (BWs) in detecting sputum negative PT. MATERIALS AND METHODS: A prospective study conducted from June 2014 to June 2015, comprising 120 patients fulfilling study criteria. Patients with respiratory symptoms and chest roentgenogram suspicious of PT with no previous history of antiTB treatment (ATT) and two spontaneous sputum smear samples negative for AFB were included in the study. Patients with active hemoptysis and sputum positive were excluded from the study. Sputum induction was done using 5–10 ml of 3% hypertonic saline through ultrasonic nebulizer taking safety precautions. All the patients underwent fiberoptic bronchoscopy after 6 h fasting on the same day. About 20 ml of normal saline instilled into the suspected pathology area and washings were taken with gentle suction. The sample processing and fluorescent staining for AFB were done in a designated microscopy laboratory. RESULTS: Of 120 smear-negative PT patients, IS smear examination detected AFB in 76 patients (63.3%) and AFB detected from BWs in 94 patients (78.5%). Smear positivity higher in cavitary and infiltrative lesions compared to consolidation and infrahilar pattern disease. CONCLUSIONS: Even though both IS and BWs procedures were valuable for the diagnosis of smear-negative TB, sputum induction with hypertonic saline should be the initial procedure of choice, which can be repeated twice/thrice in a day or 2 consecutive days. If the patient remains IS smear-negative and if the clinical probability of TB is high, starting ATT and closely monitoring patient and reserving bronchoscopy to those patients who do not improve and to exclude alternative diagnosis seems to be a practically useful approach.