Comparison between individuals by Quantiferon (QFT) test results
| QFT low negative (<0.15 IU·mL−1) | QFT borderline (0.15–0.35 IU·mL−1) | QFT low positive (0.35–0.70 IU·mL−1) | QFT high positive (≥0.70 IU·mL−1) | All | p-value | |
| Subjects n | 90 | 107 | 66 | 30 | 293 | |
| Age years | 46.1±18.7 | 48.0±19.9 | 49.8±19.5 | 43.9±17.9 | 47.4±19.3 | 0.47 |
| Males | 41/90 (45.6) | 52/107 (48.6) | 29/66 (43.9) | 15/30 (50.0) | 137/293 (46.8) | 0.91 |
| Immigrant (first generation) | 30/90 (33.3) | 54/107 (50.5) | 32/66 (48.5) | 16/30 (53.3) | 132/293 (45.1) | 0.06 |
| Incidence in country of origin ×105 per year | 54.9±57.0 | 74.7±77.0 | 135.3±129.0 | 111.9±94.4 | 89.4±95.0 | 0.002 |
| Travel to TB-endemic country | 25/90 (27.8) | 38/92 (41.3) | 29/57 (50.9) | 17/26 (65.4) | 109/265 (41.1) | 0.002 |
| Risk group (any) | 19/90 (21.1) | 36/107 (33.6) | 24/66 (36.4) | 11/30 (36.7) | 90/293 (30.7) | 0.11 |
| Comorbidities (any) | 39/90 (43.3) | 42/107 (39.3) | 31/66 (47.0) | 12/30 (40.0) | 124/293 (42.3) | 0.78 |
| Immunocompromised (any) | 17/90 (18.9) | 23/107 (21.5) | 16/66 (24.2) | 5/30 (16.7) | 61/293 (20.8) | 0.80 |
| Primary immunodeficiency | 0/90 (0) | 1/107 (0.9) | 1/66 (1.5) | 0/30 (0) | 2/293 (0.7) | 0.78 |
| HIV | 2/90 (2.2) | 4/107 (3.7) | 1/66 (1.5) | 0/30 (0) | 7/293 (2.4) | 0.77 |
| Glucocorticoids | 12/90 (13.3) | 12/107 (11.2) | 11/66 (16.7) | 4/30 (13.3) | 39/293 (13.3) | 0.77 |
| Methotrexate | 2/90 (2.2) | 6/107 (5.6) | 3/66 (4.5) | 1/30 (3.3) | 12/293 (4.1) | 0.70 |
| TNF-antagonist | 1/90 (1.1) | 1/107 (0.9) | 0/66 | 0/30 | 2/293 (0.7) | 1.0 |
| Other | 6/90 (6.7) | 7/107 (6.5) | 5/66 (7.6) | 2/30 (6.7) | 20/293 (6.8) | 0.98 |
| Reported exposure | 17/90 (18.9) | 28/107 (26.2) | 17/66 (25.8) | 9/30 (30.0) | 71/293 (24.2) | 0.52 |
| History of TB infection | 2/90 (2.2) | 7/107 (6.5) | 4/66 (6.1) | 3/30 (10.0) | 16/293 (5.5) | 0.26 |
| Active TB | 1/90 (1.1) | 3/107 (2.8) | 1/66 (1.5) | 1/30 (3.3) | 6/293 (2.0) | 0.72 |
| LTBI | 1/90 (1.1) | 4/107 (3.7) | 3/66 (4.5) | 2/30 (6.7) | 10/293 (3.4) | 0.33 |
| BCG vaccinated | 33/90 (36.7) | 47/107 (43.9) | 27/66 (40.9) | 17.30 (56.7) | 124/293 (42.3) | 0.28 |
| <1 year of age | 26/33 (78.8) | 36/47 (76.6) | 22/27 (81.5) | 15/17 (88.2) | 99/124 (79.8) | |
| ≥1 year of age | 7/33 (21.2) | 11/47 (23.4) | 5/27 (18.5) | 2/17 (11.8) | 25/124 (20.2) | |
| At least one TST available | 47/90 (52.2) | 60/107 (56.1) | 41/66 (62.1) | 24/30 (80.0) | 172/293 (58.7) | 0.054 |
| At time of QFT | 39/90 (43.3) | 48/107 (44.9) | 34/66 (51.5) | 21/30 (70.0) | 141/293 (48.1) | |
| Past or later | 15/90 (16.7) | 27/107 (25.2) | 20/66 (30.3) | 8/30 (26.7) | 70/293 (23.9) | |
| TST result at time of QFT mm | 9.1±9.3 | 12.0±8.5 | 11.7±8.5 | 18.8±6.2 | 12.1±8.9 | 0.0007 |
| TST highest of available TST mm | 9.5±8.8 | 12.1±7.8 | 12.9±9.9 | 18.7±7.4 | 12.5±9.0 | 0.0005 |
| TST highest value# | ||||||
| Positive (≥10 mm) at least once | 27/47 (57.4) | 42/60 (70.0) | 30/41 (73.2) | 22/24 (91.7) | 121/172 (70.3) | 0.027 |
| Positive (≥15 mm) at least once | 15/47 (31.9) | 20/60 (33.3) | 18/41 (43.9) | 18/24 (75.0) | 71/172 (41.3) | 0.002 |
| Positive (≥20 mm) at least once | 8/47 (17.0) | 10/60 (16.7) | 10/41 (24.4) | 14/24 (58.3) | 42/172 (24.4) | 0.0004 |
| TST category (highest value) | 0.007 | |||||
| 0 to 4 mm | 18/47 (38.3) | 10/60 (16.7) | 8/41 (19.5) | 1/24 (4.2) | 37/172 (21.5) | |
| 5 to 9 mm | 2/47 (4.3) | 8/60 (13.3) | 3/41 (7.3) | 1/24 (4.2) | 14/172 (8.1) | |
| 10 to 14 mm | 12/47 (25.5) | 22/60 (36.7) | 12/41 (29.3) | 4/24 (16.7) | 50/172 (29.1) | |
| ≥15 mm | 15/47 (31.9) | 20/60 (33.3) | 18/41 (43.9) | 18/24 (75.0) | 71/172 (41.3) | |
| QFT test results IU·mL−1 | ||||||
| NIL tube | 0.07±0.15 | 0.12±0.5 | 0.26±1.0 | 0.23±0.6 | 0.15±0.6 | 0.16 |
| PHA tube | 7.07±2.1 | 7.61±1.2 | 7.34±1.8 | 7.54±1.4 | 7.37±1.7 | 0.14 |
| TB minus NIL | 0.00±0.1 | 0.23±0.1 | 0.50±0.1 | 3.76±3.08 | 0.58±1.5 | <0.0001 |
| Reason QFT | 0.31 | |||||
| Suspected active TB | 40/90 (44.4) | 55/107 (51.4) | 31/66 (47.0) | 20/30 (66.7) | 137/293 (46.8) | |
| Screening LTBI | 50/90 (55.6) | 52/107 (48.6) | 35/66 (53.0) | 10/30 (33.3) | 156/293 (53.2) | |
| Microbiological findings of active TB (any) | ||||||
| AFB positive | 0/11 (0) | 1/22 (4.5) | 1/17 (5.9) | 0/10 (0) | 2/60 (3.3) | |
| PCR positive | 0/7 (0) | 1/14 (7.1) | 2/12 (16.7) | 0/5 (0) | 3/38 (7.9) | |
| Culture positive | 0/12 (0) | 1/23 (4.3) | 1/19 (5.3) | 0/11 (0) | 2/65 (3.1) | |
| Histology with granulomas | 2/18 (11.1)¶ | 3/33 (9.1)+ | 1/19 (5.3) | 0/6 (0) | 6/76 (7.9) | |
| Final clinical diagnosis | <0.0001 | |||||
| No TB infection | 83/90 (92.2) | 78/107 (72.9) | 5/66 (7.6) | 0/30 (0) | 166/293 (56.7) | |
| LTBI | 7/90 (7.8) | 24/107 (22.4) | 56/66 (84.4) | 26/30 (86.7) | 113/293 (38.6) | |
| Active TB | 0/90 (0) | 2/107 (1.9) | 5/66 (7.6) | 4/30 (13.3) | 11/293 (3.8) | |
| TB infection, not sure active or LTBI | 0/90 (0) | 3/107 (2.8) | 0/66 (0) | 0/30 (0) | 3/293 (1.0) |
Continuous variables are displayed as mean±sd and categorical values are displayed as numerator over denominator (%). Differences between categorical data were evaluated with Chi-squared tests or Fishers exact probability test if appropriate. Continuous data were compared between groups using one-way ANOVA or nonparametric with Mann–Whitney U- or Kruskal–Wallis tests as appropriate. Using two-sided testing, differences were considered significant at p<0.05. Statistical analysis was performed using IBM SPSS Statistics version 23 and GraphPad Prism 7. #: in case of multiple tuberculin skin tests (TST's), the highest value was used; ¶: the final diagnoses in these two patients were sarcoidosis and tertiary syphilis; +: the final diagnoses in these three patients were grey zone lymphoma, sarcoidosis as well as latent tuberculosis infection (LTBI) and peripheral multifocal chorioretinitis. TB: tuberculosis; TNF: tumour necrosis factor; BCG: bacille Calmette−Guérin; AFB: acid-fast bacilli.