Table 1 Subject characteristics

Age, years (Median, IQR)

13.6 (11.4, 15.4)

13.1 (11.4, 15.3)

13.9 (11.4, 15.4)

Sex, male

29 (63.04%)

13 (56.52%)

16 (69.57%)

Race, white

30 (71.43%) [N = 42]

16 (72.73%) [N = 22]

14 (70.00%) [N = 20]

HLA-B27 positive

23 (50.00%)

14 (60.87%)

9 (39.13%)

Hip arthritis

12 (26.09%)

8 (34.78%)

4 (17.39%)

Lower back pain

27 (58.70%)

12 (52.17%)

15 (65.22%)

Morning stiffness (> 15 min)

20 (45.45%) [N = 44]

10 (45.45%) [N = 22]

10 (45.45%) [N = 22]

Disease duration, months (Median, IQR)

11.3 (3.7, 23.7)

9.5 (2.9, 20.3)

12.0 (3.9, 36.2)

Active peripheral joint count (Median, IQR)

0.0 (0.0, 2.0)

0.0 (0.0, 2.0)

0.0 (0.0, 2.0)

Tender entheses (Median, IQR)

1.5 (0.0, 4.0)

0.0 (0.0, 5.0)

2.0 (0.0, 4.0)

Physician global (0–10; Median, IQR)

2.0 (2.0, 4.0) [N = 34]

2.0 (2.0, 4.0) [N = 21]

2.0 (1.0, 3.0) [N = 13]

Patient global (0–10; Median, IQR)

4.3 (2.0, 6.0) [N = 30]

5.0 (3.0, 6.0) [N = 19]

2.0 (1.0, 7.0) [N = 11]

Patient pain (0–10; Median, IQR)

5.0 (1.6, 7.0) [N = 30]

5.6 (2.0, 7.0) [N = 19]

3.0 (1.0, 7.0) [N = 11]

csDMARD use during follow-up

17 (36.96%)

8 (34.78%)

9 (39.13%)

Non-TNFi bDMARD use during follow-up*

4 (8.70%)

4 (17.39%)

0 (0.00%)

NSAID use during follow-up

32 (69.57%)

12 (52.17%)

20 (86.96%)