Drug resistance patterns among extra-pulmonary tuberculosis cases in a tertiary care centre in North India

Abstract

Background: xtra-pulmonary tuberculosis (EPTB) is a growing public health concern, and data on drug resistance are limited.

Material and methods: Specimens from 2468 clinically diagnosed EPTB patients received at the Intermediate Reference Laboratory (IRL) of a tertiary centre in India were subjected to Ziehl-Neelsen staining, Xpert® MTB/RIF testing, liquid culture and drug susceptibility testing (DST) using automated BACTEC MGIT™ 960™. Line-probe assay (LPA) was performed on all culture-positive isolates. Gene sequencing was performed on rifampicin-resistant/multidrug-resistant TB (RR/MDR-TB) and phenotypic/genotypic discrepant isolates.

Results: The culture positivity rate was 18.9% (483/2553). The sensitivity and specificity of Xpert in diagnosing EPTB were respectively 70.8% (95%CI 66.5-74.8) and 97.7% (95%CI 96.9-98.3), with liquid culture as the reference standard. Prevalence of RR/MDR-TB was 10.1% (49/483). Prevalence of pre-extensively drug-resistant TB (pre-XDR-TB) was 18.4% (09/49), whereas the prevalence of XDR-TB among MDR-TB patients was 2% (01/49). The sensitivity of genotypic DST for the detection of rifampicin resistance was 92.7% (95%CI 81.1-98.5) and specificity was 99.3% (95%CI 97.5-99.9), with 100% concordance between Xpert and LPA.

Conclusion: The burden of drug resistance, including M/XDR-TB, among EPTB patients is high. Novel molecular tests can help in early diagnosis and treatment to prevent disease progression and amplification of resistance.