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Comparative Study
. 2024 Jun;5(6):e520-e528.
doi: 10.1016/S2666-5247(24)00001-6. Epub 2024 Apr 9.

Xpert MTB/RIF Ultra versus mycobacterial growth indicator tube liquid culture for detection of Mycobacterium tuberculosis in symptomatic adults: a diagnostic accuracy study

Yingda L Xie  1 , Christie Eichberg  2 , Nchimunya Hapeela  3 , Elizabeth Nakabugo  4 , Irene Anyango  5 , Kiranjot Arora  1 , Jeffrey E Korte  2 , Ronald Odero  5 , Judi van Heerden  3 , Widaad Zemanay  3 , Samuel Kennedy  2 , Pamela Nabeta  6 , Mahmud Hanif  7 , Camilla Rodrigues  8 , Alena Skrahina  9 , Wendy Stevens  10 , Reynaldo Dietze  11 , Xin Liu  12 , Jerrold J Ellner  1 , David Alland  1 , Moses L Joloba  13 , Samuel G Schumacher  6 , Kimberly D McCarthy  14 , Lydia Nakiyingi  4 , Susan E Dorman  15
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Free article
Comparative Study

Xpert MTB/RIF Ultra versus mycobacterial growth indicator tube liquid culture for detection of Mycobacterium tuberculosis in symptomatic adults: a diagnostic accuracy study

Yingda L Xie et al. Lancet Microbe. 2024 Jun.
Free article

Abstract

Background: Xpert MTB/RIF Ultra (Ultra) is an automated molecular test for the detection of Mycobacterium tuberculosis in sputum. We compared the sensitivity of Ultra to that of mycobacterial growth indicator tube (MGIT) liquid culture, considered the most sensitive assay in routine clinical use.

Methods: In this prospective, multicentre, cross-sectional diagnostic accuracy study, we used a non-inferiority design to assess whether the sensitivity of a single Ultra test was non-inferior to that of a single liquid culture for detection of M tuberculosis in sputum. We enrolled adults (age ≥18 years) with pulmonary tuberculosis symptoms in 11 countries and each adult provided three sputum specimens with a minimum volume of 2 mL over 2 days. Ultra was done directly on sputum 1, and Ultra and MGIT liquid culture were done on resuspended pellet from sputum 2. Results of MGIT and solid media cultures done on sputum 3 were considered the reference standard. The pre-defined non-inferiority margin was 5·0%.

Findings: Between Feb 18, 2016, and Dec 4, 2019, we enrolled 2906 participants. 2600 (89%) participants were analysed, including 639 (25%) of 2600 who were positive for tuberculosis by the reference standard. Of the 2357 included in the non-inferiority analysis, 877 (37%) were HIV-positive and 984 (42%) were female. Sensitivity of Ultra performed directly on sputum 1 was non-inferior to that of sputum 2 MGIT culture (MGIT 91·1% vs Ultra 91·9%; difference -0·8 percentage points; 95% CI -2·8 to 1·1). Sensitivity of Ultra performed on sputum 2 pellet was also non-inferior to that of sputum 2 MGIT (MGIT 91·1% vs Ultra 91·9%; difference -0·8 percentage points; -2·7 to 1·0).

Interpretation: For the detection of M tuberculosis in sputum from adults with respiratory symptoms, there was no difference in sensitivity of a single Ultra test to that of a single MGIT culture. Highly sensitive, rapid molecular approaches for M tuberculosis detection, combined with advances in genotypic methods for drug resistance detection, have potential to replace culture.

Funding: US National Institute of Allergy and Infectious Diseases.

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Conflict of interest statement

Declaration of interests SGS was employed by FIND during conduct of the study. FIND is a not-for-profit foundation that supports the evaluation of publicly prioritised tuberculosis assays and the implementation of WHO-approved (guidance and prequalification) assays using donor grants. FIND has product evaluation agreements with several private sector companies that design diagnostics and related products for treatment of tuberculosis and other diseases. These agreements strictly define FIND’s independence and neutrality with regard to the companies whose products get evaluated and describe roles and responsibilities. DA receives income from licence payments from Cepheid to Rutgers University and reports receiving research contracts and research support from Cepheid. All other authors declare no competing interests.

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