Search

Among the challenges in controlling tuberculosis, a rapid and accurate diagnostic test for the detection of Mycobacterium tuberculosis complex (MTBc) and its resistance to first line therapies is crucial. We evaluated the performance of the Xpert MTB/RIF Ultra assay (Xpert Ultra) for the rapid detection of MTBc and rifampicin resistance (RR) in 1120 pulmonary and 461 extra-pulmonary clinical specimens and compared it with conventional phenotypic techniques. The Xpert Ultra assay detected MTBc in 223 (14.1%) samples with an overall sensitivity and specificity, using culture as the "gold standard", of 91.1% (95% CI, 85.6-95.1) and 94.5% (95% CI, 93.1-95.6), respectively. The sensitivity of the Xpert Ultra test for smear-negative extra-pulmonary specimens was high (87.1%), even higher than with smear-negative pulmonary specimens (81.8%). But this enhanced sensitivity came with a low overall specificity of smear-negative extra-pulmonary specimens (66.7%). For 73 patients, 79/1423 (3.4%) negative mycobacterial culture samples were found to be positive with Xpert Ultra. Clinical data was necessary to correctly interpret potential false-positive results, especially trace-positive results. Sensitivity of the Xpert Ultra to detect RR compared to drug susceptibility testing was 100% (95% CI, 29.2-100) and specificity was 99.2% (95% CI, 95.8-100). We concluded that the Xpert Ultra test is able to provide a reliable TB diagnosis within a significantly shorter turnaround time than culture. This is especially true for paucibacillary samples such as smear-negative pulmonary specimens and extra-pulmonary specimens., Competing Interests: No authors have competing interests.

Introduction: This study investigates the influence of Mycobacterium tuberculosis infection on immune activation biomarkers, both in HIV-infected and -uninfected subjects., Methods: Forty-eight treatment-naive HIV-infected patients and 74 HIV-uninfected subjects were recruited and divided into groups according to their M. tuberculosis infection status: latent tuberculosis infection (LTBI), active tuberculosis (TB), and no evidence of M. tuberculosis infection. The expression of cellular markers CD38 and HLA-DR on circulating CD8 T lymphocytes and the plasmatic levels of soluble markers interleukin-6, sCD14, and D-Dimer were measured and compared between groups. The HIV-infected patients with no evidence of M. tuberculosis or with LTBI who initiated antiretroviral treatment were tested again for these biomarkers once viral suppression was reached., Results: In both HIV-infected and -uninfected groups, patients with TB had higher levels of immune activation markers than subjects with LTBI and with no evidence of M. tuberculosis. Among the HIV-uninfected subjects, no significant difference in biomarker level was found between those presenting LTBI and those with no evidence of M. tuberculosis. The effect of LTBI on activation biomarkers in the HIV-infected groups was inconclusive because of the small number of individuals in the HIV+/LTBI group. sCD14 and D-Dimer levels were significantly higher in the TB-only group than in the HIV-only group., Discussion: Although TB is associated with an increase in biomarkers of immune activation, the effect of LTBI is less evident. Further investigation is warranted, and according to our results, soluble markers may offer greater sensitivity for the evaluation of M. tuberculosis-associated immune activation than cellular markers.