Performance of GeneXpert MTB/RIF for Diagnosing Tuberculosis Among Symptomatic Household Contacts of Index Patients in South Africa

• Type of Material: Article
• Authors: Kavindhran Velen, Aurum Institute; Laura J. Podewils, Denver Public Health; Sarita Shah, Emory University; James J. Lewis, London School of Hygiene & Tropical Medicine; Tiro Dinake, Aurum Institute; Gavin J. Churchyard, Aurum Institute; Mary Reichler, Independent; Salome Charalambous, Aurum Institute
• Language: English
• Date: 2021-01-19
• Publisher: Oxford University Press Inc.
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2021. Published by Oxford University Press on behalf of Infectious Diseases Society of America.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1093/ofid/ofab025
• Title of Journal or Parent Work: Open Forum Infectious Diseases
• Volume: 8
• Issue: 4
• Start Page: ofab025
• End Page: ofab025
• Grant/Funding Information: J. J. L. was funded in part by a grant jointly funded by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) (MR/K012126/1) under the MRC/DFID Concordat agreement and is also part of the EDCTP2 programme supported by the European Union.; This work was funded by the US Centers for Disease Control and Prevention (Grant TBNX-14-61028-1; in part to K. V. and S. C.).
• Keywords: TB disease; Life Sciences & Biomedicine; Burden; Assay; Microbiology; GeneXpert MTB/RIF; mycobacterial culture; household contacts; XPERT MTB/RIF; Pulmonary embolism; Children; Strategies; Science & Technology; Infectious Diseases; Specimens; Immunology; HIV
• Research Categories: Biology, Microbiology; Health Sciences, Epidemiology; Health Sciences, Immunology; Health Sciences, Public Health

Abstract

Background We describe the performance of GeneXpert MTB/RIF (Xpert) for diagnosing tuberculosis (TB) among symptomatic household contacts (HHCs) of rifampicin-resistant and drug-sensitive index cases. Methods We conducted a cross-sectional study among HHCs of recently diagnosed (<2 weeks) smear-positive and Xpert-positive index cases in the Bojanala District, South Africa. The HHCs were screened for TB symptoms; persons with ≥1 TB symptom provided 1 sputum for smear microscopy, Xpert, and mycobacterial growth indicator tube (MGIT) culture. Diagnostic test performance of Xpert was determined using MGIT as the reference standard. Results From August 2013 to July 2015, 619 HHCs from 216 index cases were enrolled: 60.6% were female, median age was 22 years (interquartile range, 9–40), and 126 (20.4%) self-reported/tested human immunodeficiency virus positive. A total of 54.3% (336 of 619) of contacts had ≥1 TB symptom (cough, fever, night sweats, weight loss), 297 of 336 (88.4%) of which provided a sputum; 289 (97.3%) had complete testing and 271 were included in the analysis. In total, 42 (6.8%) of 619 HHCs had microbiologically confirmed TB. The MGIT identified 33 HHCs as positive for Mycobacterium tuberculosis; of these, 7 were positive on Xpert resulting in a sensitivity of 21.2% (95% confidence interval [CI], 9.0–38.9), specificity of 98.3% (95% CI, 95.6–99.5), positive predictive value of 63.6% (95% CI, 30.8–89.1), and negative predictive value of 90.0 (95% CI, 85.7–93.4). Conclusions Among symptomatic HHCs investigated for TB, Xpert performed suboptimally compared with MGIT culture. The poor performance of Xpert for diagnosing TB suggests that a more sensitive test, such a Xpert Ultra or culture, may be needed to improve yield of contact investigation, where feasible.