Low Cycle Threshold Value in Xpert MTB/RIF Assay May Herald False Detection of Tuberculosis and Rifampicin Resistance: A Study of Two Cases

Jean Claude S Ngabonziza; Tom Decroo; Rodrigue Maniliho; Yves M Habimana; Armand Van Deun; Bouke C de Jong

doi:10.1093/ofid/ofab034

Low Cycle Threshold Value in Xpert MTB/RIF Assay May Herald False Detection of Tuberculosis and Rifampicin Resistance: A Study of Two Cases

Open Forum Infect Dis. 2021 Jan 21;8(2):ofab034. doi: 10.1093/ofid/ofab034. eCollection 2021 Feb.

Authors

Jean Claude S Ngabonziza^{1

2

3}, Tom Decroo^{4

5}, Rodrigue Maniliho⁶, Yves M Habimana⁷, Armand Van Deun⁸, Bouke C de Jong²

Affiliations

¹ National Reference Laboratory Division, Department of Biomedical Services, Rwanda Biomedical Centre, Kigali, Rwanda.
² Mycobacteriology Unit, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
³ Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
⁴ Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
⁵ Research Foundation Flanders, Brussels, Belgium.
⁶ Tuberculosis Laboratory, Kibagabaga Hospital, Kigali, Rwanda.
⁷ Tuberculosis and Other Respiratory Diseases Division, Institute of HIV/AIDS Disease Prevention and Control, Rwanda Biomedical Center, Kigali, Rwanda.
⁸ Independent TB Consultant, Leuven, Belgium.

Abstract

We report 2 cases for whom Xpert MTB/RIF falsely signaled rifampicin-resistant tuberculosis, based on unusually low cycle threshold and 3 of 5 probes missing. Other mycobacterial tests were negative. Further optimization of the Xpert MTB/RIF algorithm is warranted.

Keywords: Xpert MTB/RIF assay; active case finding; false detection of TB; rifampicin resistance.