Xpert®MTB/XDR Performance in Non-Sputum Samples for diagnosis of Drug-Resistant Tuberculosis at a North Indian Tertiary Care Centre

Abstract Background: Rapid diagnosis of drug-resistant tuberculosis (DR-TB) is very challenging, specifically in extra-pulmonary TB specimens. Methods: Current study was performed on non-sputum specimens. All specimens were subjected on Xpert MTB/RIF Ultra followed by Xpert MTB/XDR, Ziehl-Neelsen (ZN) Staining, liquid culture, line probe assay (LPA) and drug susceptibility testing (DST). Results: Out of 1152 non-sputum specimens, 218 were observed to be positive on Xpert MTB/RIF Ultra and were selected for further investigation. From 218 MTBC positive, Xpert MTB/XDR yielded 174 (79.8% %) positive while 25 (11.5%) were negative. On comparison with reference standards, ZN smear and culture, the sensitivity was 100% and 95.51% with specificity of 17.86% and 18.63% respectively. DST sensitivity and specificity was 84.62% and 96.61%, 83.33% and 96.88%, 50% and 98.75%, 50% and 98.72%, and 50% and 98.75% respectively for isoniazid, fluoroquinolones, amikacin, kanamycin and capreomycin in culture positive specimens. The sensitivity and specificity of Xpert MTB/XDR assay, compared with LPA (MTBDRplus and MTBDRsl) was between 94.12%-100% and 98.39%-100% respectively. Conclusion: Sensitivity and specificity of Xpert MTB/XDR matched with culture-DST and LPA results for all the tested drugs. Its placement in diagnostic algorithms with Xpert MTB/RIF Ultra under National TB Programs will enhance patient outcome by providing prompt switch to a DST guided treatment regimen.