title: The use of an automated quantitative polymerase chain reaction (Xpert MTB/RIF) to predict the sputum smear status of tuberculosis patients.
abstract: Xpert MTB/RIF-generated cycle-threshold (C(T)) values have poor clinical utility as a rule-in test for smear positivity (cut-point ≤20.2; sensitivity 32.3%, specificity 97.1%) but moderately good rule-out value (cut-point >31.8; negative predictive value 80.0%). Thus, 20% of individuals with C(T) values >31.8 were erroneously ruled out as smear-negative. This group had a significantly lower sputum bacillary load relative to correctly classified smear-positive patients (C(T) ≤ 31.8; P < .001). These data inform on public health and contact tracing strategies.
authors.affiliation: Department of Medicine, Lung Infection and Immunity Unit, Division of Pulmonology and UCT Lung Institute, University of Cape Town, South Africa.
authors.forename: Grant
authors.initials: G
authors.lastname: Theron
authors.forename: Lancelot
authors.initials: L
authors.lastname: Pinto
authors.forename: Jonny
authors.initials: J
authors.lastname: Peter
authors.forename: Hemant Kumar
authors.initials: HK
authors.lastname: Mishra
authors.forename: Hridesh Kumar
authors.initials: HK
authors.lastname: Mishra
authors.forename: Richard
authors.initials: R
authors.lastname: van Zyl-Smit
authors.forename: Surendra Kumar
authors.initials: SK
authors.lastname: Sharma
authors.forename: Keertan
authors.initials: K
authors.lastname: Dheda
mesh_terms: D001331:Automation; D001431:Bacteriological Techniques; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology*