title: Comparison of the interferon- gamma release assay and the tuberculin skin test for contact investigation of tuberculosis in BCG-vaccinated health care workers.
abstract: Health care workers are at increased risk of Mycobacterium tuberculosis infection. The tuberculin skin test (TST) is frequently false positive in BCG-vaccinated health care workers. QuantiFERON-TB GOLD (QFT-G) is a sensitive and specific interferon-gamma release assay unaffected by BCG vaccination. This study compared TST and QFT-G in the diagnosis of latent TB infection in BCG-vaccinated health care workers. 39 health care workers exposed to a smear-positive TB patient were enrolled. Initial TST was positive in 33 (84.6%) cases, but only 4 (10.2%) cases using QFT-G. TST conversion occurred in 2/6 (33.3%), compared to 4/32(12.5%), cases using QFT-G. A higher proportion of QFT converters was associated with intimate contact, although not reaching statistical significance. Face-to-face contact >1 h was significantly associated with QFT-G conversion >or=0.7 IU/ml (OR 8.63, 95%CI 1.08-69.07, p=0.04). Agreement between TST and QFT-G was 18.0%, (kappa: -0.03). Concordance between TST and QFT (>or=0.35 IU/ml) conversion was 40.0%(kappa=-0.40), and 60.0%(kappa=0.00) if QFT >or=0.7 IU/ml was used. Agreement increased with increasing TST cut-offs. TST is not useful in contact investigation among BCG-vaccinated health care workers, in an area with intermediate burden of TB. QFT may provide additional information for the diagnosis and strategic management of preventive treatment of LTBI in BCG-vaccinated health care workers in a country with intermediate burden of TB.
authors.affiliation: Section of Infectious Diseases and Microbiology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.
authors.forename: Susan Shin-Jung
authors.initials: SS
authors.lastname: Lee
authors.forename: Yung-Ching
authors.initials: YC
authors.lastname: Liu
authors.forename: Tsi-Shu
authors.initials: TS
authors.lastname: Huang
authors.forename: Yao-Shen
authors.initials: YS
authors.lastname: Chen
authors.forename: Hung-Chin
authors.initials: HC
authors.lastname: Tsai
authors.forename: Shue-Ren
authors.initials: SR
authors.lastname: Wann
authors.forename: Hsi-Hsun
authors.initials: HH
authors.lastname: Lin
mesh_terms: D006282:Health Personnel; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009163:Mycobacterium bovis / Q000276:immunology*; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D016273:Occupational Exposure; D011237:Predictive Value of Tests; D012882:Skin Tests; D014374:Tuberculin Test / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis*
chemical_list: D007371:Interferon-gamma