Accuracy of Xpert MTB/RIF Ultra for the Diagnosis of Pleural TB in a Multicenter Cohort Study

Abstract

Background: The 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.

Methods: Patients with suspected pleural TB were enrolled consecutively in four hospitals, and pleural fluids were subjected to smear, culture, and Xpert. Defrosted pleural fluid (-80°C) was examined using Xpert Ultra. Drug susceptibility testing (DST) was conducted for all of the recovered isolates.

Results: In total, 317 individuals with suspected pleural TB were recruited; 208 of them were diagnosed with pleural TB according to the composite reference standard, which was composed of clinical, laboratory, histopathologic, and radiologic examination features and ≥ 12 months of follow-up data. The direct head-to-head comparison for Mycobacterium tuberculosis detection showed that Xpert Ultra (44.23%, 92 of 208) produced a higher sensitivity than culture (26.44%, 55 of 208, P < .001), Xpert (19.23%, 40 of 208, P < .001), and smear (1.44%, three of 208, P < .001). When Xpert Ultra outcomes were integrated, the percentage of definite pleural TB cases increased from 56.25% (117 of 208) to 64.90% (135 of 208). The specificities of smear, culture, Xpert, and Xpert Ultra were 100% (84 of 84), 100% (84 of 84), 98.67% (83 of 84), and 98.67% (83 of 84), respectively. Xpert Ultra was 100% concordant with phenotype DST for the detection of RIF resistance.

Conclusions: Xpert Ultra has great potential in diagnosis of pleural TB and its RIF resistance, which could speed up the initiation of appropriate treatment.

Keywords: TB; Xpert MTB/RIF Ultra; pleural fluid.