Association of Mycobacterium tuberculosis infection test results with risk factors for tuberculosis transmission

Thara Venkatappa; Dan Shen; Aurimar Ayala; Rongxia Li; Yoseph Sorri; Rose Punnoose; Dolly Katz; Tuberculosis Epidemiologic Studies Consortium

doi:10.1016/j.jctube.2023.100386

Association of Mycobacterium tuberculosis infection test results with risk factors for tuberculosis transmission

J Clin Tuberc Other Mycobact Dis. 2023 Jun 29:33:100386. doi: 10.1016/j.jctube.2023.100386. eCollection 2023 Dec.

Authors

Thara Venkatappa¹, Dan Shen², Aurimar Ayala², Rongxia Li¹, Yoseph Sorri³, Rose Punnoose⁴, Dolly Katz¹; Tuberculosis Epidemiologic Studies Consortium

Affiliations

¹ Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, GA, USA.
² Maricopa County Department of Public Health, 1645 E Roosevelt St, Phoenix, AZ 85006, USA.
³ Seattle-King County Public Health TB Clinic, 325 9 Ave HMC Box 359776, Seattle, WA 98104, USA.
⁴ Peraton, Atlanta, 2800 Century Parkway, NE, GA 30345, USA.

Abstract

Background: Close contacts infected with Mycobacterium tuberculosis are at high risk of tuberculosis (TB) disease and a priority for preventive treatment. Three tests measure infection: two interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST). The objective of our study was to assess the association of positive test results in contacts with infectiousness of the presumed TB source case.

Methods: Contacts in a cohort study at 10 United States sites received both IGRAs (QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB (T-SPOT)) and TST. We defined test conversion as negative for all tests at baseline and positive for at least one on retest. Risk ratios (RR) and 95% confidence intervals (CI) assessed association of positive test results with increased infectiousness of the TB case-defined as acid-fast bacilli (AFB) on sputum microscopy or cavities on chest radiographs- and contact demographics.

Results: Adjusted for contacts' age, nativity, sex, and race, IGRAs (QFT-GIT RR = 6.1, 95% CI 1.7-22.2; T-SPOT RR = 9.4, 95% CI 1.1-79.1), but not TST (RR = 1.7, 95% CI 0.8-3.7), were more likely to convert among contacts exposed to persons with cavitary TB disease.

Conclusions: Because IGRA conversions in contacts are associated with infectiousness of the TB case, their use may improve efficiency of health department contact investigations by focusing efforts on those likely to benefit from preventive treatment in the United States.

Keywords: Close contacts; QuantiFERON-TB Gold In-tube; T-SPOT.TB; Tuberculin skin test.