Table 2

Effect of disease activity at baseline on the course of radiographic progression over time

Progression rate per 2-year interval*
β (95% CI)
p Value†N‡
Time1.95 (1.67 to 2.23)202
ASDAS–time interaction0.001200
 Baseline ASDAS<1.30.71 (0.08 to 1.35)14
 Baseline ASDAS≥1.3 & <2.11.30 (0.85 to 1.76)45
 Baseline ASDAS≥2.1 & ≤3.51.90 (1.44 to 2.35)88
 Baseline ASDAS>3.53.05 (2.34 to 3.76)44
BASDAI–time interaction0.023202
 Baseline BASDAI<41.41 (1.07 to 1.75)120
 Baseline BASDAI≥42.71 (2.18 to 3.23)81
CRP–time interaction0.010201
 Negative baseline CRP§1.73 (1.42 to 2.04)101
 Positive baseline CRP§2.20 (1.73 to 2.67)94
ESR–time interaction0.005201
 Baseline ESR<201.72 (1.41 to 2.04)149
 Baseline ESR≥203.01 (2.39 to 3.62)47
Patient's global assessment–time interaction0.001202
 Baseline patient's global assessment<41.35 (1.00 to 1.70)111
 Baseline patient's global assessment≥42.82 (2.36 to 3.28)90
Spinal pain–time interaction0.147201
  • *Because the dependent variable was the modified Stoke in Ankylosing Spondylitis Spine Score (mSASSS) and the independent variable was time, the regression coefficient (ß) obtained reflects the progression of mSASSS per 2 years.

  • †p Values are only shown for the interactions between time and other variables. In the presence of a significant interaction, results are stratified, and the progression in each of the subgroups is presented through the regression coefficient.

  • ‡All patients with an mSASSS evaluable at each time point independently of the availability of a 2-year progression score were included in the models.

  • §The cut-off was 10 mg/L for the Dutch patients and 5 mg/L for the Belgian and French patients.

  • ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate.