rapid diagnosis of pleural tuberculosis by xpert mtb/rif assay using pleural biopsy and pleural fluid specimens

background: early pleural tuberculosis (tb) diagnosis is particularly difficult. the aim of this study was to investigate the diagnostic accuracy of the xpert mtb/rif (xpert) (cepheid, sunnyvale, ca) assay using pleural biopsy and pleural fluid specimens in patients with suspected pleural tb but who had a negative sputum acid-fast bacilli (afb) smear. materials and 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 was used as a reference standard for sensitivity and specificity calculations. detection of rifampicin resistance was compared with the mgit method. results: of 126 evaluable patients, 55 received a diagnosis of pleural tb. the sensitivity of the xpert assay using pleural biopsy specimens for the diagnosis of pleural tb was 85.5%, and specificity was 97.2%. the sensitivity and specificity of the xpert assay in pleural fluid were 43.6% and 98.6%, respectively. the xpert assay correctly identified 90.0% of phenotypic rifampicin-resistant cases and 93.9% 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.