Table 3 Key clinical characteristics across the CLUSTER harmonised datasets and the original cohort studies

Gender

Male

929 (32.1)

776 (32.3)

1138 (31.5)

600 (35.3)

632 (32.3)

Female

1959 (67.6)

1616 (67.3)

2452 (68.0)

1101 (64.7)

1312 (67.1)

Missing

11 (0.3)

9 (0.4)

18 (0.5)

12 (0.6)

Age at JIA onset (mean, SD)

6.6 (4.3)

6.9 (4.5)

7.0 (4.5)

7.1 (4.4)

6.0 (4.1)

White ethnicity

Caucasian

2530 (87.3)

2040 (85.0)

3044 (84.4)

1365 (80.3)

1768 (90.4)

Non-Caucasian

363 (12.5)

351 (14.6)

527 (14.6)

336 (19.8)

182 (9.3)

Missing

6 (0.2)

10 (0.4)

37 (1.0)

6 (0.3)

JIA subtype at baseline

Systemic JIA

219 (7.6)

132 (5.5)

300 (8.3)

105 (6.2)

141 (7.2)

Oligoarthritis—persistent

566 (19.5)

296 (12.3)

426 (11.8)

676 (39.7)

333 (17.0)

Oligoarthritis—extended

434 (15.0)

421 (17.5)

634 (17.6)

90 (5.3)

396 (20.3)

Polyarthritis—RF negative

911 (31.4)

801 (33.4)

1173 (32.5)

322 (18.9)

657 (33.6)

Polyarthritis—RF positive

172 (5.9)

191 (8.0)

307 (8.5)

59 (3.5)

107 (5.5)

Enthesitis-related arthritis

172 (5.9)

235 (9.8)

306 (8.5)

82 (4.8)

116 (5.9)

Psoriatic JIA

203 (7.0)

156 (6.5)

227 (6.3)

114 (6.7)

107 (5.5)

Undifferentiated arthritis

138 (4.8)

109 (4.5)

103 (2.9)

173 (10.2)

15 (0.7)

Missing

84 (2.9)

60 (2.5)

132 (3.7)

80 (4.7)

84 (4.3)

Active joint count (mean, SD) at baseline

7.4 (8.2)

2.5 (4.7)

6.0 (7.9)

4.4 (6.9)

7.1 (7.8)

Limited joint count (mean, SD) at baseline

5.7 (7.6)

3.2 (6.8)

5.1 (7.4)

3.4 (5.8)

5.7 (7.4)

Uveitis

Yes

311 (10.7)

428 (17.8)

559 (15.5)

241 (14.2)

273 (14.0)

No

2073 (71.5)

1768 (73.6)

2762 (76.5)

1278 (75.1)

1291 (66.0)

Missing

515 (17.8)

205 (8.6)

287 (8.0)

182 (10.7)

392 (20.0)