Participant demographics by disease type
| Characteristic | # Missing | SLE (n=24) | JIA (n=12) | P value |
| Sex (female), n (%) | 0 | 20 (83.3) | 8 (67.6) | 0.397 |
| Age (years), mean (SD) | 0 | 15.4 (2.81) | 13.7 (2.41) | 0.119 |
| Race (white), n (%) | 0 | 6 (25.0) | 10 (90.9) | <0.001 |
| Disease duration (months), median (IQR) | 6 | 24 (39) | – | |
| Lupus nephritis (yes), n (%) | 0 | 8 (34.8) | – | |
| CNS (yes), n (%) | 0 | 1 (4.35) | – | |
| SLEDAI score, median (IQR) | 4 | 2.0 (2.0) | – | |
| Anti-RibP antibody positive (yes), n (%) | 8 | 4 (25.0) | – | |
| dsDNA Ab positive (yes), n (%) | 4 | 10 (52.6) | – | |
| C3, mean (SD) | 4 | 113.0 (30.6) | – | |
| C4, mean (SD) | 4 | 23.5 (11.3) | – |
Differences between patients with JIA and SLE for demographic characteristics were determined using Fisher’s exact test for categorical characteristics and an independent t-test or Wilcoxon rank-sum test where appropriate. Data were not available for all paediatric patients with SLE and are indicated as ‘# missing’.
CNS, central nervous system; JIA, juvenile idiopathic arthritis; RibP, ribosomal P; SLEDAI, SLE Disease Activity Index.