title: The complexities of Xpert® MTB/RIF interpretation.
abstract: The Xpert(®) MTB/RIF assay has demonstrated robust capability for diagnosing tuberculosis (TB) and rifampin (RMP) resistance. Optimal use of Xpert in diverse settings will require knowledge of challenges when interpreting the results. We present three selected cases from the United States, a low-burden TB setting, to highlight important clinical scenarios encountered with Xpert testing: rapid RMP resistance detection in a patient with pre-extensively drug-resistant TB who immigrated from the Philippines, false-positive RMP resistance detection, and Mycobacterium tuberculosis detection in a culture-negative patient. These cases demonstrate that a low pre-test probability of TB or drug-resistant TB can complicate the interpretation of the Xpert assay.
authors: <sup>*</sup>Institute for Global Health & Infectious Diseases, University of North Carolina, Chapel Hill, North Carolina, USA, <sup>†</sup>Right to Care, Johannesburg, South Africa.
authors: C K
authors: CK
authors: Lippincott
authors: <sup>‡</sup>Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill.
authors: M B
authors: MB
authors: Miller
authors: <sup>§</sup>Department of Epidemiology, University of North Carolina, Chapel Hill.
authors: A
authors: A
authors: Van Rie
authors: <sup>*</sup>Institute for Global Health & Infectious Diseases, University of North Carolina, Chapel Hill, North Carolina, USA.
authors: D J
authors: DJ
authors: Weber
authors: <sup>*</sup>Institute for Global Health & Infectious Diseases, University of North Carolina, Chapel Hill, North Carolina, USA.
authors: A C
authors: AC
authors: Sena
authors: <sup>¶</sup>Division of Infectious Diseases, Duke University, Durham, North Carolina, USA.
authors: J E
authors: JE
authors: Stout
mesh_terms: D000328:Adult; D000368:Aged; D000904:Antibiotics, Antitubercular / Q000627:therapeutic use; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D018023:HIV Seronegativity; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods* / Q000592:standards; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000302:isolation & purification; D021141:Nucleic Acid Amplification Techniques / Q000379:methods* / Q000592:standards; D012293:Rifampin / Q000627:therapeutic use; D013048:Specimen Handling; D013183:Sputum / Q000382:microbiology; D016896:Treatment Outcome; D014374:Tuberculin Test; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000188:drug therapy*; D014481:United States
chemical_list: D000904:Antibiotics, Antitubercular; D012293:Rifampin