Factors that predict for positive GeneXpert MTB/RIF on bronchoalveolar lavage samples in children with suspected tuberculosis

Background Pilot studies have reported that GeneXpert MTB/RIF (Xpert) testing of bronchoalveolar lavage (BAL) samples improves diagnostic yield and the rapid detection of drug resistance in children undergoing bronchoscopy for complicated intrathoracic tuberculosis (TB). Aim: To determine factors predictive of positive Xpert on BAL in children with suspected tuberculosis. Methods Children < 13 years undergoing bronchoscopy for suspected complicated intrathoracic TB, October 2012 to January 2014 were studied. Clinical data, including duration of TB treatment prior to bronchoscopy and chest x-ray changes, were collected. During bronchoscopy airways were evaluated for compression, severity of obstruction and lymph gland ulceration into the airways. BAL samples obtained were analysed by fluorescent smear microscopy, automated liquid culture and Xpert. Results Forty children ( median age 18 months) were studied. The median duration of TB treatment prior to bronchoscopy was 8 days . TB was confirmed in 31 (78%) by either BAL Xpert or culture. Xpert and culture were positive in 29 (73%) and 23 (58%) cases respectively. In 21 (53%) both Xpert and culture were positive. Incremental value of Xpert was 8 cases (35%); only 2 cases were culture positive but Xpert negative. The median time to culture positivity was 14 days (7-44 days). Positive Xpert was associated with lymph nodes ulcerating into the airway (p = 0.03) but not with airway obstruction , chest x-ray changes or duration of treatment <14 days . Conclusion In children with complicated pulmonary TB, Xpert on BAL increases the diagnostic yield by >35% and is associated with lymph node ulceration into the airways.