TABLE 1.

INCIDENCE OF TUBERCULIN SKIN TEST AND QUANTIFERON-TB GOLD IN-TUBE ASSAY CONVERSIONS OVER A 18-MONTH PERIOD AMONG PARTICIPANTS WHO WERE CONCORDANTLY NEGATIVE BY BOTH TESTS AT BASELINE^*

Definition of Conversion	No. Serially Tested	No. of Conversions	% Incidence of Conversions (95% CI)
TST
1. Baseline induration of < 10 mm and follow-up TST of ⩾ 10 mm, with increment of ⩾ 6 mm	147	14	9.5 (5.3–15.5)
2. Baseline induration of < 10 mm and follow-up TST of ⩾ 10 mm, with increment of ⩾ 10 mm	147	6	4.1 (1.5–8.7)
QFT
3. Baseline IFN-γ < 0.35 IU/ml and follow-up IFN-γ ⩾ 0.35 IU/ml	147	17	11.6 (6.9–17.9)
4. Baseline IFN-γ < 0.35 IU/ml and follow-up IFN-γ ⩾ 0.70 IU/ml	147	11	7.5 (3.8–13.0)
Combinations of TST and QFT
1 or 3	147	22	14.9 (9.6–21.8)
2 or 4	147	11	7.5 (3.8–13.0)
1 and 3	147	9	6.1 (2.8–11.3)
2 and 4	147	6	4.1 (1.5–8.7)

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

^*n = 147.