Rapid diagnosis of childhood pulmonary TB using bronchoalveolar lavage fluid by Xpert MTB/RIF assay

Background: Globally, the epidemic situation of tuberculosis (TB) is serious. Due to the paucibacillary nature of childhood TB, the diagnosis of childhood TB almost relies on composite clinical reference standard (CCRS). It is urgent to find a fast diagnostic method for childhood TB. We evaluated here the accuracy of Xpert MTB/RIF assay in comparison with conventional culture of the Mycobacterium tuberculosis (MTB) and the acid-fast bacillus (AFB) smear using bronchoalveolar lavage fluid (BALF) for diagnosing childhood pulmonary TB (PTB). Methods & Materials: Total267 eligible children with suspected TB were enrolled at Beijing Children's Hospital from September 2010 to July 2013. All BALF from children were tested by AFB smear, MTB culture and Xpert MTB/RIF assay. The diagnostic accuracy of three above mentioned methods were compared with CCRS. Results: Five patients (1.5%) had indeterminate results by Xpert MTB/RIF assay, thus were excluded from the diagnostic accuracy analysis. The sensitivity in diagnosing children with a clinical diagnosis of PTB for AFB smear, MTB culture and Xpert MTB/RIF assay were 7.4% (95% CI: 3.3-15.2), 25.5% (95% CI: 17.3-35.8), 52.1% (95% CI: 41.6-62.4), respectively. The sensitivity of Xpert MTB/RIF assay was significantly higher than AFB smear and MTB culture (P < 0.0001). The positive and negative predictive values of Xpert were 100% (95% CI: 90.9-100.0) and 78.9% (95% CI: 72.7-84.0), respectively, while those of MTB culture were 100% (95% CI: 82.8-100) and 70.6% (95% CI: 64.3-76.2). After the analysis of the influential factors on the positive rate of Xpert MTB/RIF assay, we found that age younger than 3 years old, BCG scar absent and TB patients contact were significantly associated with a positive Xpert MTB/RIF result. Conclusion: Xpert MTB/RIF assay have high diagnostic value in childhood PTB by using BALF sample.

Abstract licence: CC BY-NC-ND

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