title: Quantitative and qualitative QuantiFERON(®)-TB gold in-tube results among groups with varying risks of exposure to tuberculosis.
abstract: OBJECTIVE
  We sought to describe qualitative and borderline quantitative QuantiFERON(®)-TB Gold In-Tube (QFT-IT; Cellestis, Valencia, CA) results among persons screened in the context of routine reasons, employment, contact investigation, high-risk foreign-born arrivals in the United States ≤ 5 years, and high-risk United States residents >5 years.
  
  
  METHODS
  We performed a retrospective review of 3288 QFT-IT results from a clinical laboratory in the Pacific Northwest from January 2, 2008 to June 5, 2009. Interferon-γ (IFN-γ) responses were quantified as low, borderline, or high for tuberculosis (TB) antigens (IFN-γ [TB]) and a positive mitogen control (IFN-γ [mitogen]), after subtracting a background control (IFN-γ [nil]). Qualitative results were categorized as negative, positive, or indeterminate.
  
  
  RESULTS
  Quantitative values categorized as borderline, well above, or well below the cut-point were associated with qualitative results for IFN-γ (TB-nil) (χ(2) = 2913.178, degrees of freedom [df] = 4, P < .001) and IFN-γ (mitogen-nil) values (χ(2) = 2559.758, df = 4, P < .001).
  
  
  CONCLUSIONS
  Quantitative data enhance the interpretation of qualitative QFT-IT results for persons with varying risks of exposure.
authors: Department of Biobehavioral Nursing and Health Systems, University of Washington School of Nursing, Seattle, Washington 98195-7266, USA. tsimpson@uw.edu
authors: Terri
authors: T
authors: Simpson
authors: Joyce
authors: J
authors: Fox
authors: Karen
authors: K
authors: Crouse
authors: Kimberly
authors: K
authors: Field
mesh_terms: D000328:Adult; D000942:Antigens, Bacterial / Q000032:analysis*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007371:Interferon-gamma / Q000097:blood* / Q000378:metabolism; D008297:Male; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D015205:Northwestern United States / Q000453:epidemiology; D011994:Recombinant Proteins / Q000097:blood / Q000378:metabolism; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D011994:Recombinant Proteins; C554125:interferon gamma-1b; D007371:Interferon-gamma