Table 2.

Incidence of TST and QFT conversions among household contacts with concordant negative results at baseline

Criteria for conversion	Number with repeated tests*	Conversions n	Annual incidence of conversions %	95%CI
TST
Baseline TST < 10 mm, repeat TST ≥ 10 mm, plus a 6 mm increase over the baseline	80	11	13.8	7–23
Baseline TST < 10 mm, repeat TST ≥ 10 mm, plus a 10 mm increase over the baseline	80	6	7.5	3–16
QFT
Baseline IFN-γ < 0.35 IU/ml, repeat IFN-γ ≥ 0.35 IU/ml	85	18	21.2	13–31
Baseline IFN-γ < 0.35 IU/ml, repeat IFN-γ ≥ 0.35 IU/ml, plus a 30% increase over the baseline	85	18	21.2	13–31
Baseline IFN-γ < 0.35 IU/ml, repeat IFN-γ ≥ 0.35, plus an absolute increase of 0.35 IU/ml over the baseline	85	15	17.6	10–27
Baseline IFN-γ < 0.35 IU/ml, repeat IFN-γ ≥ 0.70 IU/ml	85	10	11.8	6–20

^*Only contacts with baseline concordant negative (QFT-negative/TST-negative) results were included in this analysis.

TST = tuberculin skin test; QFT = QuantiFERON-TB Gold In-Tube^®; CI = confidence interval; IFN-γ = interferon-gamma.