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Xpert Ultra in diagnosing extrapulmonary TB: accuracy and trace calls

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INTRODUCTION: Xpert Ultra (Ultra) was developed to improve the detection of TB; however, data on Ultra´s diagnostic accuracy in extrapulmonary TB (EPTB) are limited.

METHODS: In this prospective diagnostic accuracy study, 242 EPTB samples were subjected to Ultra and Xpert MTB/Rif (Xpert) testing, and these were compared with both culture and a composite gold standard.

RESULTS: Compared to culture, Ultra sensitivity and specificity using bone, cerebrospinal fluid (CSF), lymph node and tissue samples, and overall were respectively 100% and 77.3%, 75% and 100%, 87.5% and 87.5%, 100% and 87%, and 89.7% and 87.4%; in comparison to the composite gold standard, Ultra´s sensitivity and specificity were respectively 66.7% and 100%, 17.6% and 100%, 46.9% and 95.7%, 38.5% and 94.1%, and 46.2% and 96.9%. Using latent class analysis, sensitivity and specificity were respectively 94.5% and 96.3% for Ultra, 65.5% and 99.8% for Xpert, and 58.6% and 99.2% for culture. There were 22/242 (9%) trace calls on Ultra.

CONCLUSION: We found improved sensitivity for Ultra compared to Xpert, although Ultra specificity was lower, with a large number of trace results (9%).

Keywords: Ultra; extrapulmonary tuberculosis; rapid diagnostics for tuberculosis; trace calls; trace indeterminate

Document Type: Research Article

Affiliations: 1: Department of Clinical Microbiology, Christian Medical College, Vellore, India 2: Department of Infectious Diseases, Christian Medical College, Vellore, India 3: Department of Spinal Disorders, Christian Medical College, Vellore, India 4: Division of General Surgery, Christian Medical College, Vellore, India 5: Department of Biostatistics, Christian Medical College, Vellore, India

Publication date: May 1, 2022

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  • The International Journal of Tuberculosis and Lung Disease (IJTLD) is for clinical research and epidemiological studies on lung health, including articles on TB, TB-HIV and respiratory diseases such as COVID-19, asthma, COPD, child lung health and the hazards of tobacco and air pollution. Individuals and institutes can subscribe to the IJTLD online or in print – simply email us at [email protected] for details.

    The IJTLD is dedicated to understanding lung disease and to the dissemination of knowledge leading to better lung health. To allow us to share scientific research as rapidly as possible, the IJTLD is fast-tracking the publication of certain articles as preprints prior to their publication. Read fast-track articles.

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