title: Indeterminate T-SPOT.TB Test Results in Patients with Suspected Extrapulmonary Tuberculosis in Routine Clinical Practice.
abstract: BACKGROUND
  The two interferon-γ release assays such as QuantiFERON-TB Gold / In-Tube (QFT-TB) and T-SPOT.TB-are useful tools for the rapid diagnosis of tuberculosis (TB) but can yield indeterminate test results (ITRs). While some studies have identified risk factors for ITRs in the QFT-TB test, there have been few such studies for the T-SPOT.TB test. The aim of this study was to investigate the risk factors associated with ITRs in the T-SPOT.TB test.
  
  
  METHODS
  From April 2008 to August 2010, all patients with suspected extrapulmonary tuberculosis (E-TB) were enrolled in a tertiary hospital in Korea. ITR was defined as < 20 spots in the positive control well or > 10 spots in the negative control well.
  
  
  RESULTS
  Out of a total of 368 patients, 32 (8.7%, 95% CI, 6.0% to 11.7%) had ITRs in their T-SPOT.TB tests. The ITRs were due to a low mitogen response in 13 (40.6%) patients and to a high nil response in the other 19 (59.4%) patients. Statistical analysis revealed that old age, underlying diseases, immunosuppressive treatment, lymphopenia, and clinical manifestations of E-TB were not significantly associated with ITRs.
  
  
  CONCLUSIONS
  Indeterminate results in the T-SPOT.TB test are not affected by age, underlying disease, immunosuppressive treatment, lymphopenia, or clinical manifestations of E-TB, which are known risk factors for indeterminate results in the QFT-TB test.
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yu-Mi
authors.initials: YM
authors.lastname: Lee
authors.forename: Sun-Mi
authors.initials: SM
authors.lastname: Kim
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Park
authors.forename: Ki-Ho
authors.initials: KH
authors.lastname: Park
authors.forename: Sang-Oh
authors.initials: SO
authors.lastname: Lee
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Yang Soo
authors.initials: YS
authors.lastname: Kim
authors.forename: Jun Hee
authors.initials: JH
authors.lastname: Woo
authors.forename: Sung-Han
authors.initials: SH
authors.lastname: Kim
keywords: ELISPOT; Indeterminate response; Tuberculosis