Diagnostic Modalities for Detecting Extrapulmonary Tuberculosis and Resistance Patterns of Rifampicin and Isoniazid...

Tuberculosis (TB), caused by Mycobacterium tuberculosis complex, results in approximately 1.5 million annual deaths globally. Diagnosing extrapulmonary TB (EPTB) remains challenging due to the invasive nature of sample collection and limitations in conventional diagnostic sensitivity. This study evaluates the diagnostic performance of Xpert®Mycobacterium tuberculosis/Rifampicin (MTB/RIF), a nucleic acid amplification test, against direct microscopy for EPTB specimens. In addition, we compare the detection of first-line anti-tubercular drug resistance between Xpert® MTB/RIF and the MTB-DR plus line probe assay.

From January 2022, to April 2023, 2839 clinically suspected EPTB specimens were collected from patients referred to tertiary care hospitals in Gorakhpur, India. Specimens included lymph node aspirates, pleural fluid, cerebrospinal fluid, and tissue biopsies, processed according to the Indian National Tuberculosis Elimination Program protocols. Diagnostic evaluations employed microscopy (acid-fast bacilli staining), Xpert® MTB/RIF, and MTB-DR plus assays.

Of 2839 specimens, Xpert® MTB/RIF detected M. tuberculosis in 339 cases (11.9%), significantly outperforming microscopy (183 cases, 6.4%). The highest positivity rates occurred in tissue biopsies and lymph node aspirates (29%), while genitourinary TB was least frequent. Rifampicin resistance was identified in 14 cases (4.13%), all confirmed as multidrug-resistant TB (MDR-TB) by MTB-DR plus.

Xpert® MTB/RIF demonstrated superior sensitivity over microscopy, supporting its utility for EPTB diagnosis in low-resource settings. The high MDR-TB prevalence (4.13%) underscores the need for rapid molecular diagnostics to guide treatment. However, global EPTB burden estimates remain inconsistent, necessitating standardized surveillance and diagnostic protocols to improve detection accuracy and inform public health strategies.