Table 1

Baseline patient and disease characteristics of early axSpA and non-axSpA chronic back pain patients*

AxSpA (n=294) mean (SD) or n (%)Non-axSpA (n=123) mean (SD) or n (%)
Males152 (52)†30 (24)†
Age at inclusion, in years30 (8)31 (8)
Body mass index24 (5)24 (5)
Duration of back pain, in months13 (7)13 (7)
Spondyloarthritis features
Inflammatory back pain209 (71)78 (63)
Peripheral arthritis66 (22)†11 (8.9)†
Dactylitis30 (10)†1 (0.8)†
Heel enthesitis93 (32)†15 (12)†
Uveitis36 (12)†6 (4.9)†
Inflammatory bowel disease18 (6.1)8 (6.5)
Psoriasis43 (15)11 (8.9)
Family history139 (47)†72 (59)†
Good response of back pain to NSAIDs134 (46)†41 (33)†
HLA-B27 positivity214 (73)†32 (26)†
Elevated C-reactive protein (≥5 mg/L)102 (35)†28 (23)†
Positive MRI-SIJ (ASAS definition)§116 (39)†4 (3.3)†
Positive X-SIJ (mNY criteria) §15 (5.1)†0†
ASAS classification criteria§212 (72)n/a
Treatment
NSAIDs at baseline217 (74)81 (66)
NSAIDs at 2 years190 (65)†48 (39)†
NSAIDs (“ever use” during the 2 year follow-up)276 (94)†97 (79)†
csDMARDs at baseline19 (6.5)†2 (1.6)†
csDMARDs at 2 years25 (8.5)4 (3.3)
bDMARDs at baseline8 (2.7)1 (0.8)
Anti-TNF81
Other bDMARDs00
bDMARDs at 2 years57 (19)†2 (1.6)†
Anti-TNF532
Other bDMARDs40
  • *Comparisons between groups using Chi-square test for dichotomous variables and unpaired t-test for continuous variables.

  • †p-value <0.05.

  • ‡ASAS definition: presence in first or second-degree relatives of spondyloarthritis, psoriasis, uveitis, reactive arthritis or inflammatory bowel disease.

  • §According to central reading.

  • ¶1 patient with inflammatory bowel disease; 1 patient with inflammatory bowel disease and psoriasis.

  • Anti-TNF, tumour necrosis factor inhibitor; ASAS, Assessment of Spondyloarthritis International Society; axSpA, axial spondyloarthritis; bDMARDs, biologic disease modifying antirheumatic drugs; csDMARDs, conventional synthetic disease modifying antirheumatic drugs; mNY, modified New York criteria; MRI-SIJ, magnetic resonance imaging of the sacroiliac joints; n/a, not applicable; NSAIDs, nonsteroidal anti-inflammatory drugs; X-SIJ, definite damage on radiographs of the sacroiliac joints.