[Rapid diagnosis of pleural tuberculosis by Xpert MTB/RIF assay]

Abstract

Objective: Early diagnosis of pleural tuberculosis (TB) is particularly difficult. The aim of this study was to investigate the diagnostic accuracy of the Xpert MTB/RIF (Xpert) assay using pleural biopsy and pleural fluid specimens in patients with suspected pleural TB negative for sputum acid-fast bacilli (AFB) smear.

Methods: In this study, 134 sputum smear-negative suspected pleural TB patients were selected. Paired pleural fluid and pleural biopsy specimens were tested for Mycobacterium tuberculosis by standard smear-microscopy, Lowenstein-Jensen and mycobacterial growth indicator tube (MGIT) culture, and the Xpert assay. Mycobacterial culture from pleural biopsy specimens were used as a reference standard for sensitivity and specificity calculations. Detection of rifampicin resistance was compared to the MGIT method.

Results: The sensitivity of the Xpert assay using pleural biopsy specimens for the diagnosis of pleural TB was 85.5% (47/55), and the specificity was 97.2% (69/71). The sensitivity and specificity of the Xpert assay in pleural fluid were 43.6% (24/55) and 98.6% (70/71), respectively. The Xpert assay correctly identified 90.0% (10/11) of phenotypic rifampicin-resistant cases and 93.9% (31/33) of phenotypic rifampicin-susceptible cases.

Conclusion: The Xpert assay on pleural biopsy specimens may provide an accurate diagnosis of pleural TB in patients who had a negative AFB smear.