Table 2

 Variables of interest in the univariate analysis

AS (n = 21) (n (%))USpA (n = 29) (n (%))OR (95% CI)p Value
*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.
Onset <16 years10 (47.6)8 (27.6)2.39 (0.73 to 7.78)0.14
HLA-B2715/19 (78.9)15/28 (53.6)3.25 (0.86 to 12.28)0.14
Uveitis5 (23.8)1 (3.4)8.75 (0.94 to 81.64)0.08
Clinical data at onset*
Inflammatory back pain7 (29.2)17 (70.8)0.33 (0.06 to 1.79)0.14
Peripheral arthritis16 (45.7)19 (54.3)1.68 (0.48 to 5.95)0.62
Clinical data at presentation
Inflammatory back pain20 (95.2)26 (89.6)2.31 (0.22 to 23.88)0.63
Sacroiliac joint tenderness6 (37.6)10 (62.5)0.76 (0.22 to 2.57)0.66
Peripheral arthritis17 (42)24 (58)0.88 (0.21 to 3.80)1.0
Peripheral enthesitis15 (71.4)19 (65.5)1.32 (0.39 to 4.45)0.71
Dactylitis8 (38.1)10 (34.5)1.17 (0.36 to 3.76)0.79
Tarsitis6 (28.6)8 (27.6)1.05 (0.30 to 3.66)0.93
High ESR or CRP11/14 (78.5)7/16 (43.7)4.71 (0.94 to 23.68)0.11
Sacroiliac joint radiographic findings
Any low grade radiographic sacroiliitis13 (69.9)6 (20.7)6.23 (1.77 to 21.92) 0.008
    Bilateral grade 16 (28.6)1 (3.4)11.20 (1.23 to 101.89) 0.03