Detection of extensive drug resistance by the Xpert MTB/XDR assay in multidrug resistant tuberculosis cases at a tertiary care centre in northern India, and therapeutic decision making for the six-month BPaLM regimen

The Xpert MTB/XDR assay has been approved by World Health Organization (WHO) as a reflex test on sputum samples after testing for rifampicin resistance. Recently, the Union Health Ministry of India in September 2024 approved the introduction of the six-month BPaLM regimen under its National TB Elimination Program (NTEP). In this study, the Xpert MTB/XDR assay was used to detect extensive drug resistance in pulmonary and extra-pulmonary tuberculosis patients with positive result for MTBC, and RIF resistance by the Xpert MTB/RIF ULTRA assay. We also aimed to assess the eligibility of patients for the BPaLM regimen based on the drug susceptibility profile of this test in a high burden Indian setting. We conducted a single centre prospective cohort study between January 2023 to August 2024 on 42 old, and 68 new patients presenting with MDR/RR tuberculosis. A total of 110 samples (82 pulmonary and 28 extra pulmonary samples) were included in the study. The Xpert MTB/XDR assay was used to determine the susceptibilities to isoniazid, fluoroquinolones, amikacin, kanamycin, capreomycin, and ethionamide. Out of 110 samples processed, 13 samples were 'not detected' by the assay while three gave invalid results. Resistance to isoniazid, fluoroquinolones, amikacin, kanamycin, capreomycin and ethionamide was detected in 85/94 cases (90·42%), 74/94 cases (78·72%), 08/94 cases (8·5%), 13/94 cases (13·83%), 08/94 cases (8·5%), and 14/94 cases (14·89%) respectively. With the updated definitions of drug-resistant TB and high burden of fluoroquinolone resistance the Xpert MTB/XDR assay has a limited application in India. Detection of extensive drug resistance by the Xpert MTB/XDR assay in multidrug resistant tuberculosis cases at a tertiary care centre in northern India, and therapeutic decision making for the six-month BPaLM regimen.