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Abstract

The diagnosis of plural TB is challenging because of its paucibacillary feature. Even for Xpert assay, one of the most sensitive methods for TB diagnosis, plural effusion presented the lowest yield among all the specimen types.1Bates M. O'Grady J. Maeurer M. et al.Assessment of the Xpert MTB/RIF assay for diagnosis of tuberculosis with gastric lavage aspirates in children in sub-Saharan Africa: a prospective descriptive study.Lancet Infect Dis. 2013; 13: 36-42Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar Xpert-Ultra was developed to improve the sensitivity of detection for paucibacillary TB, and the increments had been reported in different type of clinical specimen.2Wang G. Wang S. Jiang G. et al.Xpert MTB/RIF Ultra improved the diagnosis of paucibacillary tuberculosis: a prospective cohort study.J Infect. 2019; 78: 311-316Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar In our diagnostic cohort study for pleural TB, Xpert-Ultra outperformed Xpert in pleural fluid specimens (44.23% vs 19.23%).3Wang G. Wang S. Yang X. et al.Accuracy of Xpert MTB/RIF Ultra for the diagnosis of pleural TB in a multicenter cohort study.Chest. 2020; 157: 268-275Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar We agree that biopsy tissue, although not included in our study, could have a better yield than pleural fluid. However, we think that molecular testing would have inferior value for tissue examination in contrast with pathologically examination, which possesses very high positivity. Additionally, we must trade off between the gain and the disadvantage of thoracoscopy for sample collecting. Thoracoscopy is an invasive examination. Local pain and subcutaneous emphysema accompany the operation frequently,4Wang Z. Xu L.L. Wu Y.B. et al.Diagnostic value and safety of medical thoracoscopy in tuberculous pleural effusion.Respir Med. 2015; 109: 1188-1192Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar and pneumothorax, local inflammation, and pleural adhesion can happen sometimes. The expenditure and inaccessibility of thoracoscopy limit its usage for patients who need it badly. In our hospital, doctors perform thoracoscopy when it is difficult but urgent to make a clear diagnosis for patient with pleural effusion. Very frequently, when malignant disease is a highly possible diagnosis. For example, when patient has no TB lesion in other locations, and the exudate had less suggestive outcomes with adenosine deaminase and lymphocyte count examinations or hemic effusion. Generally, with these preconditions, the chance that such case is pleural TB is not high. The additional benefit of Xpert-Ultra or Xpert to identify rifampicin resistance for pleural TB is disputable. Although these techniques gain credits on identifying rifampicin resistance within about 2 hours, we have to remember that the “trace” outcome of Xpert-Ultra indicates that rpoB gene is not detectable, so no resistance outcome can be made. Furthermore, “very low” positivity outcome is not trustable for its rifampicin-resistant outcome.5Ocheretina O. Byrt E. Mabou M.M. et al.False-positive rifampin resistant results with Xpert MTB/RIF version 4 assay in clinical samples with a low bacterial load.Diagn Microbiol Infect Dis. 2016; 85: 53-55Crossref PubMed Scopus (42) Google Scholar Unfortunately, for a paucibacillary specimen like pleural fluid or biopsy tissue, “very low” positivity or “trace” outcomes are common. In our cohort study, 38.04% and 42.39% of the exudates produced “very low” or “trace” semiquantitative readouts, respectively, among the Xpert-Ultra positive patients. This impairs the advantage of Xpert-Ultra in rifampin resistance identification among pleural TB. Base on these reasons, we suggest using thoracoscopic biopsy for acquiring bacteriological evidence for TB diagnosis. Xpert Ultra Is Better Than Xpert, but Using Biopsy Samples May Be Even BetterCHESTVol. 158Issue 2PreviewIn a previous issue of CHEST (February 2020), the authors need to be congratulated for conducting this relatively large study on the role of Xpert-Ultra in improving the diagnosis of pleural TB.1 The yield of Xpert Ultra from pleural fluid for detection of Mycobacterium TB was 44.23%, which was higher than culture (26.44%) and Xpert (19.23%). This is advancement in the armamentarium for the diagnosis of pleural TB. We had earlier demonstrated that if Xpert is done on pleural tissue obtained by thoracoscopic biopsy sample, there is increased diagnostic sensitivity and it exceeds the yield from pleural fluid Xpert and mycobacterial culture of pleural tissue and fluid. Full-Text PDF Accuracy of Xpert MTB/RIF Ultra for the Diagnosis of Pleural TB in a Multicenter Cohort StudyCHESTVol. 157Issue 2PreviewThe Xpert MTB/RIF (Xpert) assay has greatly improved the diagnosis of TB and identification of resistance to rifampicin (RIF). However, sensitivity of Xpert remains poor for pleural fluid detection. This study evaluated the performance of the novel next-generation Xpert MTB/RIF Ultra (Xpert Ultra) in comparison with Xpert for pleural TB diagnosis. Full-Text PDF