QuantiFERON-TB Plus (QFT-Plus) performance characteristics in different study groups
| Frequency | QFT-Plus result | Positive results in each tube | IFN-γ concentration¶ IU·mL−1 | TB2−TB1 IU·mL−1 | |||||
| Indeterminate | Negative# | Positive# | TB1 | TB2 | TB1 | TB2 | |||
| Low-risk controls | 106 | 0 | 103 (97.17) | 3 (2.83) | 2 | 1 | 0.1 (0.09–0.13) | 0.11 (0.09–0.13) | 0 (−0.01–0.01) |
| Active TB | 119 | 3 | 14 (12.07) | 102 (87.93) | 96 | 101 | 2.09 (0.83–6.52) | 2.88 (1–7.89) | 0.14 (−0.13–0.79) |
| Sex | |||||||||
| Male | 72 | 1 | 7 (9.86) | 64 (90.14) | 59 | 64 | 2.08 (0.86–6.38) | 2.91 (1.17–7.62) | 0.23 (−0.14–0.88) |
| Female | 47 | 2 | 7 (15.56) | 38 (84.44) | 37 | 37 | 2.09 (0.71–7.03) | 2.85 (0.88–7.80) | 0.11 (−0.11–0.50) |
| Smear | |||||||||
| Negative | 65 | 1 | 12 (18.75) | 52 (81.25) | 51 | 52 | 2.12 (0.89–9.51) | 2.69 (1.01–9.66) | 0.05 (−0.17–0.55) |
| Positive | 54 | 2 | 2 (3.85) | 50 (96.15) | 45 | 49 | 2 (0.67–6.04) | 3.26 (0.92–6.31) | 0.29 (0–1.16) |
| Localisation | |||||||||
| PTB | 79 | 3 | 9 (11.84) | 67 (88.16) | 62 | 66 | 1.93 (0.57–6.04) | 2.82 (0.75–6.22) | 0.26 (−0.12–0.80) |
| EPTB | 40 | 0 | 5 (12.5) | 35 (87.5) | 34 | 35 | 2.29 (1.23–10) | 2.95 (1.15–10) | 0.06 (−0.17–0.46) |
| BCG | |||||||||
| Negative | 6 | 0 | 2 (33.33) | 4 (66.67) | 4 | 4 | 1.15 (0.33–1.86) | 1.47 (0.4–2.75) | 0.07 (0.01–0.44) |
| Positive | 54 | 0 | 4 (7.41) | 50 (92.59) | 44 | 50 | 2.01 (0.9–6.57) | 2.79 (1.02–8.2) | 0.14 (−0.20–0.65) |
Data are presented as n, n (%) or median (interquartile range). IFN: interferon; TB: tuberculosis; PTB: pulmonary tuberculosis; EPTB: extrapulmonary tuberculosis; BCG: bacille Calmette–Guérin. #: percentages are based on the total number of valid tests, excluding indeterminate results.