A RECENT study highlights the clinical impact of Xpert MTB/RIF Ultra (Xpert-Ultra) in improving tuberculosis (TB) diagnosis and assessing transmission risk in low-burden settings like the UK. The research, conducted at University Hospitals of Leicester NHS Trust, evaluated the real-world utility of Xpert-Ultra against traditional methods, revealing significant diagnostic advantages, particularly for paucibacillary TB cases.
The retrospective study analysed 251 clinical specimens from 231 suspected TB patients between March 2018–February 2019. Among the cohort, 86 patients were diagnosed with TB. Compared with smear microscopy, Xpert-Ultra demonstrated a substantially higher diagnostic sensitivity (78.7% versus 24.7%, P<0.001) while maintaining comparable specificity (99.4% versus 97.5%). When compared to culture, Xpert-Ultra offered similar sensitivity (78.7% versus 71.9%) and specificity (99.4% versus 100%).
Incorporating Xpert-Ultra with culture testing significantly improved microbiologically verified TB diagnoses. For pulmonary TB, the verified diagnosis rate increased from 85.0% with culture alone to 91.7% when Xpert-Ultra was included. For extrapulmonary TB, the improvement was even more pronounced, rising from 44.8% to 75.9%.
The study also assessed the potential of Xpert-Ultra as a biomarker for transmissibility. Both smear grade and Xpert-Ultra grade were positively associated with the proportion of PTB contacts testing positive for QuantiFERON (QFT), a marker of infection. However, Xpert-Ultra outperformed smear microscopy in ruling out transmission, with a lower proportion of QFT-positive contacts among negative test cases (6.7% versus 17.7%), highlighting its superior negative predictive value.
The findings support the systematic adoption of Xpert-Ultra in low-TB-burden settings. Its ability to enhance diagnostic confirmation rates and stratify transmission risk offers a powerful tool for clinicians, improving patient outcomes and public health efforts.
Ada Enesco, EMJ
Reference
Kim JW et al. Real-world clinical utility of Xpert MTB/RIF Ultra in the assessment of tuberculosis in a low-TB-incidence, high-resource setting. BMJ Open Respir Res. 2025;12(1):e002624.
