Table 1 Demographic and disease characteristics of patients with axial spondyloarthritis (axSpA) and patients with chronic back pain (CBP) participating in the SPACE cohort

Male (n, %)

119 (43.4)

181 (28.3)

<0.001

Age (mean, SD)

30.7 (7.9)

31.4 (8.5)

0.83

HLA-B27 positive (n, %)

165 (60.7)

63 (22.1)

<0.001

Positive family history (n, %)

131 (47.8)

111 (38.8)

0.03

Duration of back pain in months (mean, SD)

13.1 (7.0)

13.5 (7.2)

0.59

Inflammatory back pain (n, %)

213 (77.7)

154 (54.0)

<0.001

Peripheral arthritis (n, %)

59 (21.6)

23 (8.1)

<0.001

Enthesitis (n, %)

91 (33.2)

21 (7.3)

<0.001

Dactylitis (n, %)

25 (9.1)

4 (1.4)

<0.001

IBD (n, %)

21 (7.7)

16 (5.6)

0.32

Psoriasis (n, %)

43 (15.7)

19 (6.6)

0.001

Uveitis (n, %)

32 (11.7)

7 (2.4)

<0.001

Tender joint count (mean, SD)

2.2 (5.0)

1.9 (3.7)

0.38

Swollen joint count (mean, SD)

0.6 (2.1)

0.1 (0.6)

0.001

CRP, mg/L (median, IQR)

3.0 (3.0–5.0)

3.7 (3.0–7.0)

0.001

CRP >5 mg/L (n, %)

113 (41.7)

70 (26.2)

<0.001

ESR, mm/h (mean, SD)

14.9 (15.8)

9.2 (11.4)

<0.001

ESR >20 mm/h (n, %)

63 (23.6)

20 (7.1)

<0.001

ASAS axSpA criteria (n, %)

172 (62.8)

48 (16.8)

<0.001

mNY criteria (n, %)

33 (14.4)

5 (2.0)

<0.001

Any DMARD use (n, %)

38 (14.0)

14 (5.1)

<0.001

NSAID use (n, %)

197 (72.4)

172 (60.8)

0.004

BASDAI (mean, SD)

4.2 (2.1)

4.7 (2.0)

0.01

Diagnosed with axSpA at 1-year follow up (n, %)

143 (52.2)

16 (5.6)

<0.001