Modelling of radiographic progression over time
| Univariable regression analysis* β (95% CI) | p Value† | N‡ | |
|---|---|---|---|
| Time (years) | 0.98 (0.84 to 1.12) | 202 | |
| Time×HLAB27 | 0.052 | 195 | |
| Progression rate if HLAB27 negative | 0.70 (0.48 to 0.90) | 31 | |
| Progression rate if HLAB27 positive | 1.03 (0.88 to 1.19) | 164 | |
| Time×gender | 0.005 | 202 | |
| Progression rate in women | 0.69 (0.57 to 0.80) | 58 | |
| Progression rate in men | 1.11 (0.93 to 1.29) | 144 | |
| Time×HLAB27 in women | 0.958 | 56 | |
| Time×HLAB27 in men | 0.044 | 139 | |
| Progression rate in men HLAB27 negative | 0.69 (0.34 to 1.03) | 19 | |
| Progression rate in men HLAB27 positive | 1.18 (0.98 to 1.38) | 120 | |
| Time×baseline mSASSS | <0.001 | 183 | |
| Progression rate in baseline mSASSS <10 | 0.69 (0.63 to 0.75) | 124 | |
| Progression rate in baseline mSASSS ≥10 | 1.44 (1.18 to 1.70) | 59 | |
| Time×baseline mSASSS in women | <0.001 | 55 | |
| Progression rate in women with baseline mSASSS <10 | 0.49 (0.42 to 0.56) | 44 | |
| Progression rate in women with baseline mSASSS ≥10 | 1.41 (0.97 to 1.85) | 11 | |
| Time×baseline mSASSS in men | <0.001 | 128 | |
| Progression rate in men with baseline mSASSS <10 | 0.81 (0.73 to 0.90) | 80 | |
| Progression rate in men with baseline mSASSS ≥10 | 1.45 (1.16 to 1.74) | 48 | |
| Time×baseline mSASSS in HLAB27 negative | 0.013 | 28 | |
| Progression rate in HLA-B27 negative with baseline mSASSS <10 | 0.75 (0.63 to 0.86) | 22 | |
| Progression rate in HLA-B27 negative with baseline mSASSS ≥10 | 0.54 (−0.20 to 1.28) | 6 | |
| Time×baseline mSASSS in HLAB27 positive | <0.001 | 149 | |
| Progression rate in HLA-B27 positive with baseline mSASSS <10 | 0.68 (0.61 to 0.75) | 99 | |
| Progression rate in HLA-B27 positive with baseline mSASSS ≥10 | 1.54 (1.27 to 1.81) | 50 | |
| Time×baseline mSASSS in men HLAB27 negative | 0.011 | 17 | |
| Progression rate in HLA-B27 negative men with baseline mSASSS <10 | 0.80 (0.63 to 0.98) | 12 | |
| Progression rate in HLA-B27 negative men with baseline mSASSS ≥10 | 0.45 (−0.40 to 1.29) | 5 | |
| Time×baseline mSASSS in men HLAB27 positive | <0.001 | 107 | |
| Progression rate in HLA-B27 positive men with baseline mSASSS <10 | 0.82 (0.72 to 0.92) | 67 | |
| Progression rate in HLA-B27 positive men with baseline mSASSS ≥10 | 1.56 (1.25 to 1.87) | 40 | |
| Time×disease duration | 0.701 | ||
| Time×symptom duration | 0.214 |
*Because the dependent variable was the mSASSS and the independent variable was time, the regression coefficient obtained reflects the progression of mSASSS per year.
†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 presented by 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.
mSASSS, modified Stoke Ankylosing Spondylitis Spine Score.