Table 1 Baseline characteristics of children with juvenile idiopathic arthritis treated with etanercepta
|  | All patients (n = 1038) | Cross-sectional groupb (n = 422) | Retrospective groupc (n = 616) | P |
|---|---|---|---|---|
Female | 781 (75.2) | 335 (79.4) | 446 (72.4) | 0.01 |
ILAR category | ||||
 Systemic arthritis | 106 (10.2) | 21 (5) | 85 (13.8) | <0.0001 |
 Persistent oligoarthritis | 139 (13.4) | 60 (14.2) | 79 (12.8) | 0.52 |
 Extended oligoarthritis | 325 (31.3) | 147 (34.8) | 178 (28.9) | 0.04 |
 RF-negative polyarthritis | 329 (31.7) | 138 (32.7) | 191 (31) | 0.56 |
 RF-positive polyarthritis | 50 (4.8) | 16 (3.8) | 34 (5.5) | 0.20 |
 Enthesitis-related arthritis | 48 (4.6) | 21 (5) | 27 (4.4) | 0.65 |
 Psoriatic arthritis | 34 (3.3) | 16 (3.8) | 18 (2.9) | 0.44 |
 Undifferentiated arthritis | 7 (0.7) | 3 (0.7) | 4 (0.6) | 1.0 |
Patients with positive ANA | 586/1028 (57) | 278 (66.5) | 308 (50.5) | <0.0001 |
Median (IQR) age at disease onset, years | 4.1 (2–8.3) | 3.5 (1.8–7.3) | 4.7 (2.1–9.1) | 0.001 |
Median (IQR) age, years | 10.1 (6.2–13.9) | 9.6 (5.8–13.6) | 10.4 (6.9–14.2) | 0.04 |
Median (IQR) disease duration, years | 3.5 (1.3–7.5) | 3.6 (1.4–7.8) | 3.3 (1.3–7.3) | 0.16 |
Patients aged < 4 years | 122 (11.8) | 54 (12.8) | 68 (11) | 0.39 |
Median (IQR) follow-up durationd, years | 2.1 (0.6–5.5) | 2.4 (0.7–6.3) | 2.1 (0.5–5.1) | 0.04 |
Treatments before ETN start | ||||
 NSAIDs | 603 (58.1) | 269 (63.7) | 334 (54.2) | 0.002 |
 Systemic corticosteroids | 527 (50.8) | 198 (46.9) | 329 (53.4) | 0.04 |
 Intra-articular corticosteroids | 579 (55.8) | 263 (62.3) | 316 (51.3) | 0.0004 |
 Methotrexate | 930 (89.6) | 387 (91.7) | 543 (88.1) | 0.07 |
 Other synthetic DMARDs | 187 (18) | 48 (11.4) | 139 (22.6) | <0.0001 |
 Other biologic agents | 53 (5.1) | 18 (4.3) | 35 (5.7) | 0.31 |
Concomitant therapies during ETN administration | ||||
 Systemic corticosteroids | 267 (25.7) | 93 (22) | 174 (28.2) | 0.02 |
 Intra-articular corticosteroids | 257 (24.8) | 98 (23.2) | 159 (25.8) | 0.34 |
 Methotrexate | 749 (72.2) | 311 (73.7) | 438 (71.1) | 0.36 |
 Other synthetic DMARDs | 73 (7) | 17 (4) | 56 (9.1) | 0.002 |