GeneXpert on patients with human immunodeficiency virus and smear-negative pulmonary tuberculosis

Vietnam is a high-prevalence country for tuberculosis (TB). Xpert MTB/RIF is a novel PCR-based diagnostic test that is substantially more sensitive for detecting M. tuberculosis than traditional smear-based techniques. However, locally-derived evidence of Xpert MTB/RIF in HIV-infected people is limited. This study evaluates the performance of the Xpert MTB/RIF in HIV-infected patients with smear-negative pulmonary TB (SNTB). This was a cross-sectional study in 3 hospitals. The performance of Xpert MTB/RIF was compared with the reference standard of liquid culture and phenotypic drug-susceptibility testing for rifampicin (RIF) resistance. Out of 123 patients, the median age was 37.0 (IQR: 32.0-41.0) and 81.3% were male. The area under the receiver operating characteristic curve, sensitivity (Se) and specificity (Sp) of Xpert MTB/RIF for pulmonary TB diagnosis were 0.72 (95% confidence interval [CI]: 0.63-0.81), 66.7% (95%CI: 54.8-77.1) and 77.1% (95%CI: 62.7-88.0), respectively, while Se and Sp of Xpert MTB/RIF in detecting RIF resistance were 50.0 (11.8-88.2) and 86.4% (95%CI: 72.7-94.8). The performance of Xpert MTB/RIF in HIV-infected patients with SNTB for the diagnosis of TB and RIF-resistance was low. Further studies are required to evaluate the results of Xpert MTB/RIF assay in HIV-infected patients with SNTB and the role of Xpert repetition on the same specimens.