Publication date: Sep 01, 2025
Background Accurate and timely detection of Mycobacterium tuberculosis (MTB) and associated drug resistance is vital for effective tuberculosis (TB) control, especially in high-burden countries like India. In recent years, molecular assays have significantly improved TB diagnostics. This study evaluates and compares the diagnostic accuracy of the Xpert MTB/RIF assay and the GenoType MTBDRplus version 2. 0 line probe assay (LPA) in identifying MTB and rifampicin resistance in both pulmonary and extrapulmonary clinical specimens. Methodology Over an 18-month period, 500 clinical specimens, comprising 257 pulmonary and 243 extrapulmonary samples, were analyzed using Ziehl-Neelsen staining, Lowenstein-Jensen culture, and the Xpert MTB/RIF assay. All samples positive for MTB by either culture or Xpert (n = 124) were further assessed using LPA. Cases with discordant rifampicin resistance findings between molecular assays were validated using phenotypic drug susceptibility testing (DST) using the MGIT 960 SIRE system. Results Among the 124 MTB-positive cases, pulmonary samples accounted for 90 (72. 6%), and extrapulmonary samples accounted for 34 (27. 4%). Xpert MTB/RIF detected MTB in 121 cases, showing a sensitivity of 95. 3% and specificity of 86. 9% compared to culture. Culture positivity was 48 (53. 3%) in pulmonary and 16 (44. 4%) in extrapulmonary specimens. Valid LPA results were obtained in 119 samples, with MTB detected in 86 cases, yielding an overall sensitivity of 72. 3%. Detection rates were higher in smear-positive (48, 92. 3%) compared to smear-negative samples (38, 52. 7%). Rifampicin resistance was identified by Xpert in 28 (22. 5%) cases, with 7 (8. 1%) instances of discordance between Xpert and LPA results. Of these, five were concordant with LPA and two with Xpert upon phenotypic DST. Conclusions The Xpert MTB/RIF assay demonstrated excellent sensitivity, particularly in smear-negative and extrapulmonary samples. LPA showed better concordance with phenotypic DST for rifampicin resistance but was less effective in smear-negative cases. These findings highlight the complementary roles of molecular and phenotypic methods in enhancing the diagnosis of TB and detecting resistance.
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| Concepts | Keywords |
|---|---|
| High | mycobacterium tuberculous |
| Month | pulmonary |
| Mtbdrplus | rr-tb (rifampicin-resistant tuberculosis) |
| Mycobacterium | |
| Tuberculosis |
Semantics
| Type | Source | Name |
|---|---|---|
| drug | DRUGBANK | Rifampicin |
| disease | MESH | Tuberculosis |
| pathway | KEGG | Tuberculosis |
| disease | IDO | assay |
| disease | IDO | drug susceptibility |
| drug | DRUGBANK | Dihydrostreptomycin |
| drug | DRUGBANK | Tropicamide |