title: Sensitivity of C-Tb: a novel RD-1-specific skin test for the diagnosis of tuberculosis infection.
abstract: C-Tb, a novel Mycobacterium tuberculosis and 6-kDa early secretory antigenic target/10-kDa culture filtrate protein (ESAT-6/CFP-10)-specific skin test, has high specificity in bacille Calmette-Guerin-vaccinated healthy controls. However, the sensitivity of C-Tb has hitherto not been determined. The objective was to determine the sensitivity of C-Tb in patients with active tuberculosis (TB) in comparison with the tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube (QFT-GIT).C-Tb and TST were randomly administered in a double-blinded fashion to one or the other forearm in 253 patients with active TB with or without HIV co-infection. QFT-GIT testing was performed prior to skin testing.Using a receiver operating characteristic curve-derived cut-point of 5 mm, C-Tb sensitivity was similar to QFT-GIT (73.9 (95% CI 67.8-79.3) versus 75.1 (95% CI 69.3-80.2)), and similar in HIV-infected and HIV-uninfected patients (76.7 (95% CI 69.0-83.3) versus 69.5 (95% CI 59.2-78.5)). However, sensitivity was significantly diminished in HIV-infected patients with CD4 counts <100 cells·mm(-3). C-Tb and QFT-GIT combined had significantly higher sensitivity than C-Tb alone (p<0.0001). C-Tb was safe with no significant adverse events. The 5 mm cut-point corresponded to that found in the previously published specificity study (TESEC-04).C-Tb has similar sensitivity compared with QFT-GIT for the diagnosis of M. tuberculosis infection. Sensitivity was reduced only in HIV-infected patients with severe immunosuppression. Further studies in different settings are required to validate the proposed 5 mm cut-point.
authors.affiliation: Dept of Infectious Diseases Immunology, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Soren T
authors.initials: ST
authors.lastname: Hoff
authors.affiliation: Lung Infection and Immunity Unit, Division of Pulmonology and UCT Lung Institute, Dept of Medicine, University of Cape Town, Cape Town, South Africa.
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Peter
authors.affiliation: Lung Infection and Immunity Unit, Division of Pulmonology and UCT Lung Institute, Dept of Medicine, University of Cape Town, Cape Town, South Africa.
authors.forename: Grant
authors.initials: G
authors.lastname: Theron
authors.affiliation: Lung Infection and Immunity Unit, Division of Pulmonology and UCT Lung Institute, Dept of Medicine, University of Cape Town, Cape Town, South Africa.
authors.forename: Mellissa
authors.initials: M
authors.lastname: Pascoe
authors.affiliation: Dept of Vaccine Development, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Pernille N
authors.initials: PN
authors.lastname: Tingskov
authors.affiliation: Dept of Vaccine Development, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Aggerbeck
authors.affiliation: Dept of Vaccine Development, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kolbus
authors.affiliation: Dept of Infectious Diseases Immunology, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Ruhwald
authors.affiliation: Dept of Infectious Diseases Immunology, Statens Serum Institut, Copenhagen, Denmark Joint senior authors.
authors.forename: Peter
authors.initials: P
authors.lastname: Andersen
authors.affiliation: Lung Infection and Immunity Unit, Division of Pulmonology and UCT Lung Institute, Dept of Medicine, University of Cape Town, Cape Town, South Africa Joint senior authors keertan.dheda@uct.ac.za.
authors.forename: Keertan
authors.initials: K
authors.lastname: Dheda
mesh_terms: D000293:Adolescent; D000328:Adult; D060085:Coinfection; D004311:Double-Blind Method; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D012372:ROC Curve; D013019:South Africa; D014374:Tuberculin Test / Q000592:standards*; D014376:Tuberculosis / Q000175:diagnosis*; D055815:Young Adult