Performance of QuantiFERON-TB Gold and Tuberculin Skin Test Relative to Subjects' Risk of Exposure to Tuberculosis

Among a large group of college students tested for latent tuberculosis infection, we found that QuantiFERON-TB Gold In-Tube (QFT-GIT) was less specific than tuberculin skin test (TST). Risk-stratified interpretation, which is currently used with TST, improved specificity of QFT-GIT. Background. Performance of QuantiFERON-TB Gold In-Tube (QFT-GIT) and tuberculin skin test (TST) has not been compared in a US college population with varying risk of tuberculosis exposure. Methods. We performed a retrospective chart review of students tested for tuberculosis at the University of Pennsylvania Student Health Service between 2009 and 2011. We stratified students into high-, low-, and no-risk categories for exposure to tuberculosis and compared QFT-GIT and TST performance in risk groups adjusting demographic characteristics. Results. During the study period, 15 936 tuberculosis tests were performed in 9483 college students. Coming from a tuberculosis-endemic country was the only risk factor significantly associated with having a positive result (odds ratio [OR] 12.9; 95% confidence interval [CI], 10.2–16.5). Test specificity was higher for TST than QFT-GIT (99.7% vs 91.4%; P < .0001). Application of a higher threshold for positivity improved comparability of QFT-GIT with TST in the low-risk group (adjusted OR [AOR] 1.2; 95% CI, .4–3.3) but not in the high-risk group (AOR .4; 95% CI, .3–.5). Conclusions. QFT-GIT was less specific than TST. Our findings support the use of TST for US college students who need tuberculosis testing and the use of risk-stratified interpretation for students who are tested with QFT-GIT.