Table 1 Clinical and demographic characteristics of study participants

Age at Diagnosis, years, Mean ± SD

10.4 ± 4.3

6.0 ± 4.4

<0.001

Age at Collection, years, Mean ± SD

13.3 ± 3.8

9.7 ± 4.4

<0.001

Gender- Female, N (%)

69 (89.6 %)

81 (65.3 %)

<0.001

Race, N (%)

Caucasian

44 (57.1 %)

105 (84.7 %)

<0.001

African American

23 (29.9 %)

12 (9.7 %)

Other^a

10 (13.0 %)

7 (5.6 %)

Hispanic, N (%)

13 (16.9 %)

11 (8.9 %)

0.089

ILAR, N (%) (n = 199)

Systemic

0 (0.0 %)

13 (10.6 %)

0.003

RF (+)

59 (76.6 %)

0 (0.0 %)

<0.001

RF (−)

5 (6.5 %)

46 (37.7 %)

<0.001

Oligo Persistent

4 (5.2 %)

30 (24.6 %)

<0.001

Oligo Extended

4 (5.2 %)

12 (9.8 %)

0.386

ERA

1 (1.3 %)

20 (16.4 %)

<0.001

Psoriatic

1 (1.3 %)

0 (0.0 %)

0.766

Other

3 (3.9 %)

1 (0.8 %)

0.178