Evaluation of diagnostic accuracy of Xpert® ultra and Xpert MTB/RIF for detection of tuberculosis among pulmonary tuberculosis suspects in Pune, India

Tuberculosis (TB), particularly pulmonary TB remains a significant global health challenge. The traditional diagnostic methods are time-consuming, laborious, and require a well-equipped laboratory setting and trained personnel. Early diagnosis is essential to control the spread of TB infection by enabling timely initiation of appropriate treatment. The present study was conducted to evaluate the diagnostic accuracy of the Xpert® Ultra assay. We evaluated the diagnostic performance of the Xpert® Ultra assay with the Xpert assay and conventional gold standard methods for diagnosing pulmonary TB from sputum samples. A total of 481 participants with clinical symptoms of TB were included in the study. Sputum samples were collected from study participants and processed for ZN staining, MGIT liquid culture, and both versions of GeneXpert assays. The Xpert® Ultra assay detected Mtb in culture-positive samples with 92.0 % (95 % CI: 85.2-96.6), whereas the Xpert® MTB/RIF assay showed a sensitivity of 81.0 % (95 % CI: 72.6-87.6 %). This 11.0 % absolute increase in sensitivity (95 % CI: 4.0-18.0 %; p = 0.01) shows the superiority of the Xpert® Ultra assay over its predecessor, the Xpert® MTB/RIF assay. The specificity was 96.1 % (366/381, 95 % CI: 93.2-98.2 %) for the Xpert® Ultra assay and 98.7 % (376/381, 95 % CI: 96.8-99.6 %) for the Xpert® MTB/RIF assay, with a difference of 2.6 % (95 % CI:5.2 to 0.0; p = 0.05). "Trace" results, accounting for 5.2 % of all positive results, were the primary source of false positives and were frequently linked to prior TB history. Such results require clinical correlation and culture confirmation before the initiation of treatment.