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Need for caution when interpreting Xpert® MTB/RIF results for rifampin resistance among children

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BACKGROUND: Recommended by the World Health Organization as an initial diagnostic test for TB in children, Xpert® MTB/RIF is widely implemented in many countries, including Kenya.

METHODS: Three hundred HIV-positive and negative children (<5 years) were enrolled in Kisumu County, Kenya, from October 2013 to August 2015. Multiple specimen types were collected from each child and tested using Xpert, liquid culture, and phenotypic drug susceptibility testing (DST). Samples positive for rifampin (RIF) resistance on Xpert were tested using line-probe assay and sequencing.

RESULTS: Of 32 children with bacteriologically confirmed TB, 27 had positive Xpert results. Of these, 3/27 (11%, 95% CI 4–28) had RIF resistance detected on Xpert, but not by phenotypic DST, line-probe assay, or sequencing. For these three children, five Xpert tests showed RIF resistance; all five tests had semi-quantitative “very low” results and delay or absence of probe D signal, whereas no Xpert results with higher semi-quantitative results showed RIF resistance. All three children responded well to standard TB treatment.

CONCLUSIONS: False RIF resistance may be detected in pediatric specimens. Further study is needed to determine if false RIF resistance is associated with low bacterial load.

Keywords: Xpert MTB/RIF; children; cycle threshold; false-positive; rifampin resistance; tuberculosis

Document Type: Research Article

Affiliations: 1: Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya; 2: U.S. Centers for Disease Control and Prevention (CDC), Atlanta, GA USA 3: CDC, Kisumu, Kenya 4: Division of Infectious Diseases, Boston Children´s Hospital, Boston, MA, Department of Pediatrics, Harvard Medical School, Boston, MA, USA, Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK

Publication date: November 1, 2021

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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.

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