Editorial
The Good, the Bad and the Ugly of the Next-Generation Xpert Mtb/Rif® Ultra Test for Tuberculosis DiagnosisPros y contras de la prueba xpert MTB/RIF® ultra de nueva generación para diagnosticar la tuberculosis

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  • Xpert MTB/RIF Ultra assay for the detection of Mycobacterium tuberculosis in people with negative conventional Xpert MTB/RIF but chest imaging suggestive of tuberculosis in Dhaka, Bangladesh

    2022, International Journal of Infectious Diseases
    Citation Excerpt :

    As per the manufacturer, Ultra detects lower concentrations (15 colony forming units (CFU)/ml) of Mycobacterium tuberculosis (MTB) which approximates the limit of detection of MTB in liquid culture, a fold improvement over that of Xpert (112 CFU/ml) (Berhanu et al., 2018). It is expected that Ultra's higher sensitivity will improve the diagnosis of paucibacillary forms of TB such as those occurring in young children, certain forms of extra-pulmonary, or in HIV-associated disease (Berhanu et al., 2018; García-Basteiro et al., 2017; Kabir et al., 2021; Opota et al., 2019b; Zijenah, 2018). However, given the lower level of MTB DNA detection by Ultra, particularly with 'trace calls' where it has been suggested to repeat the test, there remains a concern about false-positive results.

  • Comparison of Xpert MTB/RIF (G4) and Xpert Ultra, including trace readouts, for the diagnosis of pulmonary tuberculosis in a TB and HIV endemic setting

    2020, International Journal of Infectious Diseases
    Citation Excerpt :

    The threshold for detection with Xpert Ultra was ∼1-log CFU better over Xpert MTB/RIF (12 CFU/ml versus 130 CFU/ml) (Chakravorty et al., 2017). However, this improvement in sensitivity comes at the cost of decreased specificity (Garcia-Basteiro et al., 2017). However, there are several gaps in our knowledge about the utility of Xpert Ultra in HIV-infected persons, in those with a history of previous TB, and the epidemiology of trace readouts has been poorly studied.

  • Xpert MTB/RIF Ultra and Xpert MTB/RIF for diagnosis of tuberculosis in an HIV-endemic setting with a high burden of previous tuberculosis: a two-cohort diagnostic accuracy study

    2020, The Lancet Respiratory Medicine
    Citation Excerpt :

    Different strategies for interpreting results that are Ultra positive and categorised as trace have been explored to improve specificity.14 However, the optimal strategy, including stratification by tuberculosis treatment history, remains unclear.3,15 If, as considered by some tuberculosis programmes, traces are not reported as positive, the benefits offered by Ultra over Xpert will be reduced (Xpert relies only on rpoB amplification).

  • Xpert MTB/Ultra assay: Handle with care

    2020, Journal of Infection
  • Evaluation of Xpert MTB/RIF Ultra performance for pulmonary tuberculosis (TB) diagnosis in a city with high TB incidence in Brazil

    2020, Respiratory Medicine
    Citation Excerpt :

    Overall, sensitivity of the Xpert MTB/RIF Ultra was 5% higher than that of Xpert MTB/RIF (95%CI + 2.7, +7.8), and specificity was 3.2% lower (95%CI -2.1, −4.7). The higher sensitivity is notably important in the diagnosis of HIV-associated TB, pediatric TB, and extrapulmonary TB forms [5,7,12]. In contrast, specificity is lower in patients with a history of treated TB, probably due to detection of dead bacilli, especially in the new trace semiquantitative category [7,12].

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