Mycobacterium tuberculosis infection, immigration status, and diagnostic discordance: A comparison of tuberculin skin test and quantiFERON®-TB gold in-tube test among immigrants to the U.S

Objective. We used a recent source of nationally representative population data on tuberculosis (TB) infection to characterize concordance between the tuberculin skin test (TST) and the QuantiFERON®-TB Gold In-Tube (QFT-GIT) blood test for immigrants in the United States. Methods. We used TB screening data from the 2011-2012 National Health and Nutrition Examination Survey to examine concordance between the TST and QFT-GIT-an interferon-gamma release assay (IGRA) blood test-for 7,097 U.S. natives, naturalized citizens, and noncitizens. Results. Consistent with prior findings, one in five immigrants in the survey was identified with latent TB infection (LTBI), a rate 14 times higher than for U.S. natives. We also found higher rates of discordant TST/IGRA results among immigrants than among U.S. natives. Unadjusted discordance between TST and IGRA was 3% among U.S. natives (weighted N55,684,274 of 191,179,213) but ranged up to 19% for noncitizens (weighted N53,722,960 of 19,377,147). Adjusting for age, sex, and race/ethnicity, noncitizens had more than nine times the odds of having a positive TST result but negative QFT-GIT result compared with U.S. natives. Conclusions. Our findings suggest that whether and how either of these tests should be deployed is highly context sensitive. Significant discordance in test results when used among immigrants raises the possibility of missed opportunities for harm reduction in this already at-risk population. However, we found little distinction between the tests in terms of diagnostic outcome when used in a U.S. native population, suggesting little benefit to the adoption and use of the QFT-GIT test in place of TST on the basis of test performance alone for this population.