Reflex Xpert MTB/XDR Testing of Residual Rifampicin-Resistant Specimens: A Clinical Laboratory-Based Diagnostic Accuracy and Feasibility Study in South Africa.

Background: The World Health Organization-approved Xpert MTB/XDR test detects and resistance to isoniazid, fluoroquinolones, ethionamide, and injectable drugs directly in specimens. This pragmatic, laboratory-based study assessed the diagnostic accuracy and feasibility of a reflex testing approach, where Xpert MTB/XDR was performed on residual specimens previously processed for Xpert MTB/RIF Ultra.

Methods: Routine respiratory specimens, processed for Xpert MTB/RIF Ultra, were stored in sample reagent buffer at 2°C-8°C.

Bedaquiline resistance in patients with drug-resistant tuberculosis in Cape Town, South Africa: a retrospective longitudinal cohort study.

Background: Bedaquiline is a life-saving tuberculosis drug undergoing global scale-up. People at risk of weak tuberculosis drug regimens are a priority for novel drug access despite the potential source of Mycobacterium tuberculosis-resistant strains. We aimed to characterise bedaquiline resistance in individuals who had sustained culture positivity during bedaquiline-based treatment.

Xpert MTB/RIF Ultra on contaminated liquid cultures for tuberculosis and rifampicin-resistance detection: a diagnostic accuracy evaluation.

Background: Xpert MTB/RIF Ultra (Ultra) is a widely used rapid front-line tuberculosis and rifampicin-susceptibility testing. Mycobacterium Growth Indicator Tube (MGIT) 960 liquid culture is used as an adjunct but is vulnerable to contamination. We aimed to assess whether Ultra can be used on to-be-discarded contaminated cultures.

To Test or Not? Xpert MTB/RIF as an Alternative to Smear Microscopy to Guide Line Probe Assay Testing for Drug-Resistant Tuberculosis.

Xpert MTB/RIF (Xpert) revolutionized tuberculosis (TB) diagnosis. Laboratory decision making on whether widely-used reflex drug susceptibility assays (MTBDR, first-line resistance; MTBDR, second-line) are conducted is based on smear status, with smear-negative specimens often excluded. We performed receiver operator characteristic (ROC) curve analyses using bacterial load information (smear microscopy grade, Xpert-generated semi-quantitation categories and minimum cycle threshold [C] values) from Xpert rifampicin-resistant sputum for the prediction of downstream line probe assay results as "likely non-actionable" (no resistance or susceptible results generated).