Performance of the Xpert® MTB/RIF assay in the rapid diagnosis of tracheobronchial tuberculosis using bronchial washing fluid.

Abstract

ObjectiveTo assess the diagnostic value of the Xpert® MTB/RIF (GeneXpert) assay for tracheobronchial tuberculosis (TBTB) using bronchial washing fluid (BWF).MethodsThis retrospective study enrolled patients suspected of having TBTB and patients with non-TB pulmonary disease as controls. BWF were used to undertake acid-fast bacillus (AFB) smears, the GeneXpert assay and the Lӧwenstein–Jensen (LJ) culture method. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were compared among BWF AFB smears, BWF GeneXpert and the BWF LJ culture method.ResultsA total of 130 patients with TBTB and 102 patients with non-TB pulmonary disease were enrolled in the study. Sputum AFB smears were positive in 62 of 130 patients (47.7%) with TBTB. Using the clinical diagnosis of TBTB as the gold standard, the sensitivity, specificity, PPV and NPV of the three methods using BWF were as follows: 93.1%, 99.0%, 99.2% and 91.8% for BWF GeneXpert; 73.1%, 100.0%, 100.0% and 74.5% for BWF LJ cultures; 53.8%, 99.0%, 98.6% and 62.7% for BWF AFB smears. The diagnostic yield of BWF GeneXpert was significantly higher compared with BWF cultures for type III and IV TBTB.ConclusionThe Xpert® MTB/RIF assay using BWF exhibited higher sensitivity than bacteriological diagnostic methods and was particularly useful for the early diagnosis of smear-negative TBTB.