title: QuantiFERON-TB Gold in-tube testing for tuberculosis in healthcare professionals.
abstract: OBJECTIVE
  To assess the performance of the QuantiFERON-TB Gold in-tube (QFT-GIT) assay for tuberculosis (TB) screening using a convenience sample from among a population of healthcare provider (HCP) employees of a hospital.
  
  
  METHODS
  For the individuals in our cohort, we reviewed occupational health records, including TB risk factors, and the results of QFT-GIT testing. We considered a QFT-GIT result of greater than 0.35 IU/mL to be positive; when we obtained a positive result from a specimen from a particular individual, we repeated testing on a fresh specimen from that individual.
  
  
  RESULTS
  Of the 758 HCP employees whose specimens we screened, 439 had negative QFT-GIT results with negative TB risk factors and 268 had a negative QFT-GIT result but had positive TB risk factors. QFT-GIT results were positive in 47 subjects. Of the positive participants, 12 had a mean TB antigen value (antigen minus nil stimulated concentrations [Ag-Nil]) of 0.61 on initial testing and had a negative result on repeat testing, 22 had a TB Ag-Nil of 1.19 on initial testing and had a positive result on repeat testing (P = .01).
  
  
  CONCLUSIONS
  The QFT-GIT assay is useful for screening HCPs. However, false-positive results occur, particularly in a borderline zone of less than 1 IU/ml. Re-evaluation by repeat testing of fresh specimens from the same individual should be considered in subjects whose specimens test within the low-level positive cutoff.
authors: Department of Infectious Disease, Children's Mercy Hospitals and Clinics, Kansas City, MO;
authors: Gina
authors: G
authors: Weddle
authors: Department of Pathology and Laboratory Medicine, Children's Mercy Hospitals and Clinics, Kansas City, MO; mhamilton@cmh.edu.
authors: Marilyn
authors: M
authors: Hamilton
authors: Allergy/Immunology Laboratory, Children's Mercy Hospitals and Clinics, Kansas City, MO;
authors: Deborah
authors: D
authors: Potthoff
authors: Department of Occupational Health, Children's Mercy Hospitals and Clinics, Kansas City, MO.
authors: Deb
authors: D
authors: Rivera
authors: Department of Infectious Disease, Children's Mercy Hospitals and Clinics, Kansas City, MO;
authors: Mary Anne
authors: MA
authors: Jackson
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D059425:Interferon-gamma Release Tests; D016272:Occupational Health; D012189:Retrospective Studies; D012307:Risk Factors; D014376:Tuberculosis / Q000175:diagnosis*
keywords: QuantiFERON; children’s hospital; healthcare employee; screening; tuberculosis