Sensitivity and specificity of Gene Xpert Ultra in extrapulmonary tuberculosis (EPTB).

Introduction: Gene Xpert sensitivity is low in paucibacillary conditions like extrapulmonary tuberculosis (EPTB); to overcome that, Gene Xpert Ultra was introduced. This study aims to assess Gene Xpert Ultra's diagnostic accuracy in EPTB.

Methods: This prospective observational study was conducted at Apollo Hospital, Greams Road, Chennai, Tamil Nadu, India, from May 2022 to April 2023. A total of 200 patients, 39 (19.5%) abdominal, 61 (30.5%) musculoskeletal, one (0.5%) bone marrow, 50 (25%) lymph nodes, 11 (5.5%) CNS, two (1%) upper airway, one (0.5%) cardiovascular, and 35 (17.5%) pleural cases were enrolled. Samples were analyzed for Gene Xpert Ultra, MGIT culture, cytology, and histopathology wherever feasible with tuberculosis. Tissue sampling was performed rather than bodily fluid in all cases except in CNS and abscess, where CSF and pus were analyzed, respectively. Gene Xpert Ultra was then compared with MGIT culture and Composite reference standard (CRS).

Results: The pooled sensitivity and specificity of Gene Xpert Ultra were 96.18% and 18.84% against MGIT and 94.30% and 100% against CRS. The lowest sensitivity (90%) was in CSF, and the highest (100%) was in pleura against CRS.

Conclusion: Gene Xpert Ultra has high sensitivity and specificity in tissue samples in various system involvements. This study recommends employing Gene Xpert Ultra in EPTB and further encourages tissue sample testing.