Table 2.

Annual Risk of QuantiFERON and Tuberculin Skin Test Conversion and Reversion Risks by Study Surveillance Group

	QFT	TST	Cohen’s κ*
Nonintensive group
Conversion risk	13.6%	13.6%	0.72
Reversion risk	4.3%	4.5%	0.14
Intensive group†
Conversion risk	14.5%	12.3%	0.76
Reversion risk	5.7%	3.8%	0.12
Combined
Conversion risk	14.0%	13.0%	0.74
Reversion risk	5.1%	4.1%	0.12

Definition of abbreviations: QFT = QuantiFERON TB Gold In-Tube test; TST = tuberculin skin test.

^*Cohen’s κ was calculated by comparing Day 720 QFT and TST results among participants with concordant results at baseline.

^†Conversion and reversion risks in the intensive surveillance group were calculated using a two-step TST, with negative results at Days 0 and 90 considered negative. When considering Day 0 results only, the TST conversion and reversion risks were 17.9 and 2.8%, respectively, and the respective κ values were lower at 0.69 and 0.08.