Characteristics of the population included in prospective analyses at the time of QuantiFERON-TB Gold (QFT) testing*
| Baseline characteristic | Norwegian-born | Foreign-born | Total | P values |
| Total population† | 25 457 (57) | 19 418 (43) | 44 875 (100) | |
| Sex (male) | 11 426 (45) | 7941 (41) | 19 367 (43) | <0.001 |
| Age (years), median (IQR) | 44 (26–60) | 31 (25–40) | 36 (25–53) | <0.001 |
| Age group (years) | <0.001 | |||
| <5 | 940 (4) | 372 (2) | 1312 (3) | |
| 5–14 | 1600 (6) | 1144 (6) | 2744 (6) | |
| 15–34 | 6651 (26) | 10 452 (54) | 17 103 (38) | |
| 35–64 | 11 578 (46) | 6810 (35) | 18 388 (41) | |
| >65 | 4688 (18) | 640 (3) | 5328 (12) | |
| Observation time after QFT (months), median (IQR)‡ | 43 (31-60) | 43 (28-63) | 43 (29-61) | <0.001 |
| Healthcare level of QFT request | <0.001 | |||
| Primary healthcare (screening) | 7004 (28) | 11 736 (60) | 18 740 (42) | |
| Outpatient hospital clinic | 5982 (24) | 4577 (24) | 10 559 (24) | |
| Paediatric in-/outpatient unit | 1179 (5) | 471 (2) | 1650 (4) | |
| Inpatient, internal medicine | 3409 (13) | 1391 (7) | 4800 (11) | |
| DMARD-relevant medical unit§ | 7880 (31) | 1242 (6) | 9122 (20) | |
| Identified underlying disease, any¶ | 13 774 (54) | 2984 (15) | 16 758 (37) | <0.001 |
| HIV infection | 295 (1) | 610 (3) | 905 (2) | |
| Diabetes | 1376 (5) | 704 (4) | 2080 (5) | |
| Malignant neoplasm | 1657 (7) | 312 (2) | 1969 (4) | |
| Chronic renal disease | 589 (2) | 180 (1) | 769 (2) | |
| Solid organ transplant | 140 (0.6) | 46 (0.2) | 186 (0.4) | |
| DMARD-relevant diagnosis§ | 11 498 (45) | 1530 (8) | 13 028 (29) | |
| Malnutrition | 514 (2) | 79 (0.5) | 593 (1) | |
| Alcohol/opiate dependence syndrome | 389 (1.5) | 60 (0.3) | 449 (1) | |
| Iatrogenic immunosuppression, any** | 6311 (25) | 634 (3) | 6945 (15) | <0.001 |
| Long-term glucocorticosteroids†† | 256 (1) | 41 (0.2) | 297 (0.6) | |
| Antineoplastic agents | 1040 (4) | 71 (0.4) | 1111 (2) | |
| Selective immunosuppressants | 539 (2) | 57 (0.3) | 596 (1) | |
| TNF-alpha inhibitors | 925 (4) | 78 (0.4) | 1003 (2) | |
| Interleukin inhibitors | 31 (0.1) | 6 (0) | 37 (0.1) | |
| Systemic calcineurin inhibitors | 182 (0.7) | 42 (0.2) | 224 (0.5) | |
| Other immunosuppressants‡‡ | 4072 (16) | 412 (2) | 4484 (10) | |
Data are presented as n (%) or median (IQR).
*At time of first QFT when several tests were administered.
↵†Demographic data were obtained from Statistics Norway.
↵‡From time of QFT until event (TB) or LTBI treatment, death, emigration or study end.
↵§Includes rheumatological, dermatological, neurological and gastroenterological medical units/diseases.
↵¶Includes medical risk factors that were present prior to or at the time of QFT testing. Sources for classifications are ICD-10/NCMP codes from the Norwegian Patient Registry and ATC codes from the Norwegian Prescription Database.
↵**Includes outpatient prescriptions for immunosuppressive treatment, obtained from the Norwegian Prescription Database. Prescriptions within 6 months prior to QFT testing were included.
↵††Systemic corticoids≥15 mg/day for ≥1 month.
‡‡Methotrexate (L04A×03) accounted for 79% of prescriptions.
ATC, anatomical therapeutic chemical; DMARD, disease-modifying antirheumatic drug; ICD-10, International Classification of Diseases, 10th revision; LTBI, latent TB infection; NCMP, Norwegian Classification of Medical Procedures; TNF, tumour necrosis factor.