Table 1.

Proportion of Household Contacts Classified as Resistant to Mtb Infection Using Varying Definitions for Infection and Exposure

	All HHCs			Highly Exposed HHCs
Criteria for Defining HHC as a resistera	HHCs Included	n (%) Resistant, TST Cutoff <5 mm	n (%) Resistant, TST Cutoff 0 mm	HHCs Included	n (%) Resistant, TST Cutoff <5 mm	n (%) Resistant, TST Cutoff 0 mm
TST- and IGRA2-b	572	77 (13.5)	71 (12.4)	263	29 (11.0)	26 (10.0)
TST- and IGRA2-; TST- and IGRA1- and IGRA2 missing	616	101 (16.4)	93 (15.1)	285	38 (13.3)	35 (12.3)
All tests negative or any test negative while others missing	898	188 (20.9)	180 (20.0)	415	63 (15.2)	60 (14.5)

Abbreviations: HHC, household contact; IGRA1, interferon gamma release assay at baseline; IGRA2, interferon gamma release assay after 1-year follow-up; Mtb, Mycobacterium tuberculosis; TB, tuberculosis; TST, tuberculin skin test at baseline.

^a Age ≥5 was a required criterion for inclusion in the analysis population. No evidence of active TB was required criteria for classifying a HHC as a resister in all definitions.

^b IGRA2 was only performed if IGRA1 was negative or missing.