Chaudhary J, Chawla DS, Gupta V, Singh A, Aggarwal M. Diagnostic Efficacy of New Xpert Ultra for Extrapulmonary Tuberculosis Using Culture and Composite Reference Standard.
Int J Appl Basic Med Res 2023;
13:224-229. [PMID:
38229732 PMCID:
PMC10789468 DOI:
10.4103/ijabmr.ijabmr_348_23]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 10/07/2023] [Accepted: 10/13/2023] [Indexed: 01/18/2024] Open
Abstract
Introduction
Xpert Ultra (Cepheid, USA) is recently introduced with an extra category of trace-positive results and higher sensitivity for tuberculosis (TB) diagnosis.
Objective
The objective of the study was to assess the diagnostic accuracy of Xpert Ultra for extrapulmonary samples using culture and composite reference standard (CRS) as the gold standard.
Materials and Methods
In a 1-year (March 2021-22) prospective observational study, samples of suspected extrapulmonary TB (EPTB) patients were subjected to Ziehl-Neelsen staining, culture, and Xpert Ultra (Cepheid, Sunnyvale, CA) tests. Relevant clinical and treatment information was noted. The diagnostic accuracy of Xpert Ultra compared with culture and CRS was calculated.
Results
Out of 1720 suspected patients of EPTB, 223 (13%), predominantly males 135 (60%), with a mean age of 41.46 ± 19.81 years, were diagnosed as TB positive following CRS criteria. The maximum cases were of pleural TB (35.4%), followed by central nervous system TB (17.9%), gastrointestinal TB (17.5%), and lymph node TB (12.1%). Of all samples, 150 (8.7%) were microbiologically confirmed, including 141 detected by Xpert ultra, 67 culture positive, and only 16 smear positive. Among the Xpert Ultra-positive samples, 35 showed trace results, including six false-positive results. Considering culture and CRS as the gold standard, the sensitivity (86.57%, 59.64%) and specificity (94.98%, 99.47%) of Xpert Ultra were calculated, respectively. Rifampicin resistance was detected in 1 (0.70%) sample.
Conclusion
Diagnosis of EPTB is a challenge and Xpert Ultra may detect TB at a very early stage. However, it is essential to rule out false-positive results. Additional studies are needed on Xpert Ultra to interpret trace results better.
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