Table 2 Variables of interest in the univariate analysis.
| AS (n = 21) | USpA (n = 29) | OR (95% CI) | p Value | |
|---|---|---|---|---|
| (n (%)) | (n (%)) | |||
| Onset <16 years | 10 (47.6) | 8 (27.6) | 2.39 (0.73 to 7.78) | 0.14 |
| HLA‐B27 | 15/19 (78.9) | 15/28 (53.6) | 3.25 (0.86 to 12.28) | 0.14 |
| Uveitis | 5 (23.8) | 1 (3.4) | 8.75 (0.94 to 81.64) | 0.08 |
| Clinical data at onset* | ||||
| Inflammatory back pain | 7 (29.2) | 17 (70.8) | 0.33 (0.06 to 1.79) | 0.14 |
| Peripheral arthritis | 16 (45.7) | 19 (54.3) | 1.68 (0.48 to 5.95) | 0.62 |
| Clinical data at presentation | ||||
| Inflammatory back pain | 20 (95.2) | 26 (89.6) | 2.31 (0.22 to 23.88) | 0.63 |
| Sacroiliac joint tenderness | 6 (37.6) | 10 (62.5) | 0.76 (0.22 to 2.57) | 0.66 |
| Peripheral arthritis | 17 (42) | 24 (58) | 0.88 (0.21 to 3.80) | 1.0 |
| Peripheral enthesitis | 15 (71.4) | 19 (65.5) | 1.32 (0.39 to 4.45) | 0.71 |
| Dactylitis | 8 (38.1) | 10 (34.5) | 1.17 (0.36 to 3.76) | 0.79 |
| Tarsitis | 6 (28.6) | 8 (27.6) | 1.05 (0.30 to 3.66) | 0.93 |
| High ESR or CRP | 11/14 (78.5) | 7/16 (43.7) | 4.71 (0.94 to 23.68) | 0.11 |
| Sacroiliac joint radiographic findings | ||||
| Any low grade radiographic sacroiliitis | 13 (69.9) | 6 (20.7) | 6.23 (1.77 to 21.92) | 0.008 |
| Bilateral grade 1 | 6 (28.6) | 1 (3.4) | 11.20 (1.23 to 101.89) | 0.03 |
*Mean age at onset was 20.9 (8.4) years in ankylosing spondylitis and 19.8 (9.3) years in undifferentiated spondyloarthritis (p = 0.39).
†Mean age at presentation was 27.3 (8.2) years in ankylosing spondylitis and 26.0 (9.3) years in undifferentiated spondyloarthritis (p = 0.61).
AS, ankylosing spondylitis; CI, confidence interval; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; OR, odds ratio; USpA, undifferentiated spondyloarthritis.