High proportion of indeterminate quantiferon-tb gold in-tube results in an inpatient population is related to host factors and preanalytical steps

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Abstract

Background. QuantiFERON-TB Gold In-Tube test (QFT-GIT) can be used as an alternative to tuberculin skin testing (TST) for the targeted testing of latent tuberculosis. Due to many shortcomings with TST, QFT-GIT usage is increasing. QFT-GIT implementation in the inpatient setting remains unclear. Methods. We retrospectively identified patients admitted to a tertiary care academic center who received either a TST or a QFT-GIT in the 18 months prior to and after QFT-GIT implementation in March 2012. Risk factors associated with indeterminate results were evaluated. Results. The proportion of inpatients receiving a test for tuberculosis infection doubled following QFT-GIT implementation (1.4% vs 2.9%). After QFT-GIT became available, 75% of tested people received a QFT-GIT and 25% received a TST. We found indeterminate test results in 19.8%. Independent predictors of indeterminate results were female sex (adjusted odds ratio [AOR], 1.64), lymphopenia (AOR, 2.21), hypoalbuminemia (AOR, 6.81) and sample collection by nonphlebotomists (AOR, 3.0, vs phlebotomists). Of patients who had indeterminate results, 42% had a subsequent indeterminate result on repeat testing. All indeterminate results were due to a low mitogen response. Conclusions. QFT-GIT testing in the inpatient setting is associated with a high proportion of indeterminate results that is associated with host factors and preanalytical errors. Careful selection of patients to be tested and training on sample processing for QFT-GIT testing should be considered to decrease indeterminate results.

Original languageEnglish (US)
JournalOpen Forum Infectious Diseases
Volume1
Issue number2
DOIs
StatePublished - 2014

Keywords

  • IGRA
  • TB diagnostics
  • TB screening

ASJC Scopus subject areas

  • Oncology
  • Clinical Neurology

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