title: Cumulative False-Positive QuantiFERON-TB Interferon-γ Release Assay Results.
abstract: Despite reports of unreliability, the QuantiFERON-TB interferon-γ release assay is increasingly used for the annual screening of individuals at risk for latent tuberculosis. Continued use of the QuantiFERON-TB assay suggests the need for more definitive evidence of its reproducibility and accuracy.
  
  
  
  To examine reproducibility and the accumulation of false-positive test results when the QuantiFERON-TB is repeated annually and to examine the validity of confirming positive test results with the performance of a second QuantiFERON-TB.
  
  
  
  We performed a retrospective, longitudinal evaluation of results from serial screening of a cohort of emergency responders from 2001 to 2013.
  
  
  
  Results of tuberculin tests and QuantiFERON-TB tests performed annually as part of a mandated first responder examination were retroactively reviewed. In this population, positive results occurred in new individuals each year. QuantiFERON-TB results were positive in 80 of 557 tuberculin test-negative individuals examined annually for a maximum of 7 years. Only 10 individuals with initially positive results remained positive when the test was repeated the next year, and 9 of these 10 were QuantiFERON-TB-negative within 3 years. The number of individuals with a positive result increased annually, and, after 7 years, 32 (27.4%) of 117 people had a positive result.
  
  
  
  When viewed in the context of the extensive literature documenting unreliable QuantiFERON-TB test performance, our findings of frequent, cumulative, sporadic, and irreproducible positive results support discontinuing the use of the QuantiFERON-TB assay for the diagnosis of latent tuberculosis in low-risk populations.
authors.affiliation: 1 Contra Costa County Employee Occupational Medicine Clinic, Department of Health Services, Division of Public Health, Martinez, California.|2 Veterans Affairs Northern California Health Care System, Martinez, California.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Gamsky
authors.affiliation: 3 East Bay Institute for Research and Education, Rancho Cordova, California.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lum
authors.affiliation: 4 Contra Costa County Public Health Laboratory, Department of Health Services, Martinez, California; and.
authors.forename: Melody
authors.initials: M
authors.lastname: Hung-Fan
authors.affiliation: 3 East Bay Institute for Research and Education, Rancho Cordova, California.|2 Veterans Affairs Northern California Health Care System, Martinez, California.
authors.forename: Jon A
authors.initials: JA
authors.lastname: Green
mesh_terms: D000328:Adult; D002140:California; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000592:standards*; D055985:Latent Tuberculosis / Q000175:diagnosis*; D008137:Longitudinal Studies; D008297:Male; D008403:Mass Screening / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014374:Tuberculin Test / Q000379:methods
keywords: interferon-γ release tests; latent tuberculosis; reproducibility of results; tuberculin; tuberculin test