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Table 1 Baseline characteristics of chronic back pain patients suspected of axial spondyloarthritis included in the ASAS cohort

From: Do ethnicity, degree of family relationship, and the spondyloarthritis subtype in affected relatives influence the association between a positive family history for spondyloarthritis and HLA-B27 carriership? Results from the worldwide ASAS cohort

Characteristics Data (N = 594)
Age at baseline, years 33.7 (11.7)
Male sex 276 (46%)
Duration of back pain, yearsa 7.1 (9.0)
Self-reported ethnicity
 White 348 (59%)
 Asian 214 (36%)
 Otherb 32 (5%)
IBP (according to experts’ definition) 301/532 (57%)
Good response to NSAIDsc 274 (46%)
Peripheral arthritisd 197 (33%)
Enthesitisd 241 (41%)
AAUd 53 (9%)
Dactylitisd 23 (4%)
Psoriasisd 22 (4%)
IBDd 8 (1%)
Positive family history according to ASAS definition 135 (23%)
 Positive family history of AS 87 (15%)
 Positive family history of AAU 7 (1%)
 Positive family history of ReA 8 (1%)
 Positive family history of IBD 12 (2%)
 Positive family history of Psoriasis 36 (6%)
Total number of SpA-related diseases in first- or second-degree relatives
 Number of patients with one disease 120 (20%)
 Number of patients with two diseases 15 (3%)
Total number of family members with SpA-related diseases
 Number of patients with one relative 102 (17%)
 Number of patients with two relatives 30 (5%)
 Number of patients with three relatives 3 (1%)
Total number of patients with positive family history in
 First-degree relatives only 100 (17%)
 Second-degree relatives only 25 (4%)
 Both first- and second-degree relatives 10 (2%)
HLA-B27 positivity 310 (52%)
Elevated CRP/ESR 185 (31%)
Definite radiographic sacroiliitise 119/593 (20%)
Presence of active inflammation on MRI-SI 189/424 (45%)
Number of SpA featuresf,g 2.4 (1.6)
Clinical diagnosis of axSpAh 368 (62%)
  1. Abbreviations: AAU Acute anterior uveitis, AS Ankylosing spondylitis, ASAS Assessment of SpondyloArthritis international Society, (ax)SpA (Axial) spondyloarthritis, CRP C-reactive protein, ESR Erythrocyte sedimentation rate, HLA-B27 Human leukocyte antigen B27, IBD Inflammatory bowel disease, IBP Inflammatory back pain, MRI-SI Magnetic resonance imaging of the sacroiliac joints, NSAID Nonsteroidal anti-inflammatory drug, ReA Reactive arthritis, SI Sacroiliac joint
  2. Results are presented as mean ± SD unless specified otherwise
  3. a < 5% missing values
  4. b Self-reported ethnicity was missing for five patients, who are included in this category, and other self-reported ethnicities are black, East Indian, Hispanic/Latino, mixed, or Turkish
  5. c Back pain not present anymore or is much better 24–48 hours after a full dose of NSAID
  6. d Past or present condition
  7. e Grade ≥ 2 bilateral or grade ≥ 3 unilateral
  8. f Excluding HLA-B27 carriership and imaging
  9. g < 20% missing values
  10. h Level of confidence regarding the diagnosis is ≥ 6