1660. Quantitative QuantiFERON-TB Gold In-Tube Test Result and Tuberculosis Risks, Outcome of Repeat Testing, and Clinical Assessment of Latent Tuberculosis
Session: Poster Abstract Session: Mycobacterial Infections
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
  • LTBI Poster4.pdf (282.3 kB)
  • Background: Tuberculosis (TB) remains an important cause of morbidity and mortality worldwide. QuantiFERON-TB Gold In-Tube (QFT-GIT) identifies latent tuberculosis infection (LTBI) which can aid efforts to prevent TB but its positive predictive value is imperfect in settings with low TB incidence.

    Methods: We performed a medical record review of all patients from 1 January 2011 to 25 February 2012 with positive QFT-GIT tests obtained at our facility in a setting with TB incidence <2/100,000. We abstracted reasons for testing, reported risk(s) for LTBI, ancillary LTBI testing, and clinical interpretation of the QFT-GIT (LTBI or not LTBI). These variables were then correlated to the quantitative result.

    Results: 145 patients were identified (54% female, median age 44). Median positive QFT-GIT results were significantly higher in patients interpreted as having LTBI (1.60 vs 0.75, p < 0.001) including the subset of patients for whom the provider was unaware of the quantitative result (N=110, 1.74 vs 0.75, p < 0.005) No single or combination of LTBI risk factors was significantly associated with higher median QFT-GIT results, but end stage renal disease (ESRD) was associated with lower values (0.49 vs 1.41, p < 0.001.) A complete review of risk factors was only clearly documented in 17% of cases, but there was no difference in the distribution of LTBI cases compared to those with incomplete documentation (67% vs 71%, p 0.67.) In the subset of patients for whom additional testing was performed (N=67), there was a significant correlation between the initial QFT-GIT test and the follow up test (2.89 for positives vs 0.76 for negatives, p < 0.001). The results of additional testing did not change clinical decision making in 10 of the cases. Overall 17 of the patients tested had no identifiable risk factors, 11 of whom still received treatment for LTBI.

    Conclusion: Our data suggests that, in a low prevalence setting, the quantitative QFT-GIT result may aid the diagnosis of LTBI which in turn might prevent unnecessary treatment and follow up testing. Continuing education is additionally warranted to reduce testing in cases where it would not alter clinical decision making.

    Scott Crabtree, MD, Infectious Disease, Dartmouth Hitchcock Medical Center, Lebanon, NH, Richard Zuckerman, MD, MPH, Dartmouth-Hitchcock Medical Center, Lebanon, NH and Elizabeth Talbot, MD, Infectious Disease and International Health, Dartmouth Hitchcock Medical Center, Lebanon, NH


    S. Crabtree, None

    R. Zuckerman, None

    E. Talbot, None

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