Diagnostic performance of Xpert® MTB/RIF Ultra among smear-negative pulmonary tuberculosis cases in southwestern Oromia, Ethiopia.

OBJECTIVES: Diagnosing smear-negative pulmonary tuberculosis poses significant challenges due to the low bacillary load, which often results in delayed diagnosis and poor treatment outcomes. This study evaluated the diagnostic performance of Xpert MTB/RIF Ultra (Xpert Ultra) in detecting Mycobacterium tuberculosis among patients with presumptive smear-negative pulmonary tuberculosis in southwestern Oromia, Ethiopia. METHODS: A hospital-based cross-sectional study was conducted at Jimma University Medical Center from January to June 2023. A total of 255 sputum samples were collected from patients with presumptive pulmonary tuberculosis (TB) who had negative results on two sputum smear microscopy results for acid-fast bacilli. All samples were tested using Xpert Ultra and Mycobacterial Growth Indicator Tube 960 (MGIT 960) culture. Sensitivity, specificity, and positive and negative predictive values of Xpert Ultra were calculated using MGIT 960 culture as the reference standard. RESULTS: Among 255 patients with presumptive smear-negative pulmonary TB, Xpert Ultra detected Mycobacterium tuberculosis in 38 (14.9%), whereas MGIT 960 culture identified 41 (16.1%) cases. Compared with MGIT 960 culture, Xpert Ultra demonstrated a sensitivity of 90.2% (95% confidence interval [CI]: 76.9-97.3%) and a specificity of 99.5% (95% CI: 97.3-100.0%). The positive and negative predictive values were 97.4% (95% CI: 83.9-99.6%) and 98.1% (95% CI: 95.2-99.2%), respectively. CONCLUSION: The Xpert Ultra offers a rapid, sensitive, and specific method for diagnosing active TB in patients with presumptive smear-negative pulmonary TB cases. Expanding access to Xpert Ultra could improve the management of smear-negative pulmonary TB.