Performance of the MTBDRsl Line probe assay for rapid detection of resistance to second-line anti-tuberculosis drugs and ethambutol in China

This study aimed to assess the performance of the GenoType MTBDRsl Line Probe Assay (LPA) for the detection of resistance to levofloxacin, amikacin, capreomycin and ethambutol on sputum specimens. Sputum samples from patients with smear positive multidrug-resistant tuberculosis, identified with GenoType MTBDRplus LPA, were further evaluated using the MTBDRsl LPA, while phenotypic drug susceptibility testing was used as control. Sputa with discordant outcomes were assessed by gene sequencing. 189 cases were included. The interpretability of the MTBDRsl LPA was 96.8%. The sensitivity and specificity of the MTBDRsl test were 82.5% and 91.5% for levofloxacin, 52.6% and 99.2% for amikacin, 58.1% and 97.7% for capreomycin, and 70.8% and 93.3% for ethambutol respectively. For the diagnosis of extensively drug-resistant tuberculosis, the sensitivity and specificity were 56.1% and 100%. The MTBDRsl LPA presents a specific screening tool to detect resistance to several key second-line anti-tuberculosis drugs and ethambutol in smear positive specimens.