Assessment of Conventional and Molecular Methods in the Routine Management of Tuberculosis in a High Tuberculosis Burden Setting

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Abstract
Background and aims: India is a high-burden tuberculosis region and a drug-resistance hotspot. Despite numerous reports of pulmonary tuberculosis (PTB) cases, there needs to be more literature available on the importance of diagnostic methods in the case of extrapulmonary tuberculosis (EPTB). A prospective study was carried out from July 2017 to June 2018 to compare the efficacy of conventional and molecular methods in detecting PTB and EPTB cases. Methods: 1000 presumptive PTB and 412 EPTB cases were subjected to staining (Ziehl-Neelson and fluorescent staining), culture, GeneXpert, and line probe assay. Results: The sensitivity, specificity, and strength of association, i.e., kappa (k) value of LED-FM, ZN, and GeneXpert, were calculated using standard formulae using solid culture as the gold standard. The sensitivity of GeneXpert in smear-positive/culture-positive PTB was comparable with the smear-negative/culture-positive PTB cases (95.7% Vs. 87.5%) with an overall sensitivity and specificity of 90.5% and 90.1% in EPTB cases, respectively. However, sensitivity was lower for pleural fluid (75%) and tissues (85.7%). In pulmonary instances, 10% (6.7% RIF + INH resistant and 3.3%INH monoresistant) drug resistance was observed, and no drug resistance was found in extra-pulmonary samples. Conclusion: Among conventional methods, Fluorescent staining is more sensitive than Ziehl-Neelson (ZN) staining, while the sensitivity of GeneXpert varies w.r.t type of sample using culture positivity as the gold standard. The present study suggests the promotion of universal DST for all individuals with TB to control drug-resistant tuberculosis.

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