The Xpert MTB/RIF Ultra assay has improved sensitivity over the standard Xpert MTB/RIF particularly for which patient population?
- A Patients with MDR-TB on second-line therapy
- B Smear-negative and paucibacillary TB, including HIV co-infected individuals ✓
- C Extra-pulmonary TB involving bone and joint
- D Patients with treatment-naïve smear-positive pulmonary TB
Correct answer: B. Smear-negative and paucibacillary TB, including HIV co-infected individuals
Explanation
The Ultra version uses two molecular beacons (IS6110 and IS1081 targets) plus multicopy amplification, achieving a lower limit of detection of 16 colony-forming units/mL versus 114 CFU/mL for standard Xpert. This enhanced sensitivity is particularly beneficial for smear-negative, paucibacillary specimens (common in HIV-TB co-infection, where bacillary load may be very low). The trade-off is marginally reduced specificity due to detection of non-viable bacilli after treatment. For smear-positive cases, standard Xpert and Ultra perform similarly.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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