Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose: It has been previously shown that spinal mobility in ankylosing spondylitis (AS) is associated with the level of inflammation of the spine. However an association does not necessarily imply causation and only longitudinal studies can evaluate if a change in an outcome measure translates into a subsequent change in the associated measure. Our aim was to study the relationship between change in MRI spinal inflammation and change in spinal mobility in patients with AS, taking potential confounders into account.
Methods: Baseline, 24- and 102-week data of a random 80% sample of the AS Study for the Evaluation of Recombinant Infliximab Therapy (ASSERT) cohort were used. Spinal mobility was expressed by the linear version of the Bath AS Metrology Index (BASMI), spinal inflammation by the AS spinal MRI activity (ASspiMRI-a) score and clinical disease activity by the Bath AS disease activity index or by the AS disease activity score (ASDAS). BASMI, ASspiMRI-a, BASDAI and ASDAS change scores were calculated (from baseline to 24 weeks and from 24 weeks to 102 weeks). The longitudinal association between change in BASMI (dependent variable) and change in ASspiMRI-a (independent variable) was investigated using generalised estimating equations (GEE). Potential confounders (change in BASDAI, change in ASDAS, change in C-reactive protein, gender, age, disease duration, body mass index, HLA-B27 status and baseline modified Stoke AS Spine Score (mSASSS)) and interactions were tested.
Results: In total 199 patients and 367 visits were analysed (31 patients did not have complete 102-week data). After taking potential confounders into account, multivariable GEE analysis showed that change in ASspiMRI-a, change in BASDAI and baseline mSASSS are longitudinally associated with change in BASMI (table 1, model A). When change in BASDAI was replaced by change in ASDAS in the multivariable model, only change in ASDAS and baseline mSASSS were significantly associated with change in BASMI, but not change in ASspiMRI-a (table 1, model B).
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Table 1. GEE models for change in BASMI |
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Model A (with change in BASDAI) |
Model B (with change in ASDAS) |
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Independent variable |
B (95% CI), p-value |
B (95% CI), p-value |
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Change in ASspiMRI-a |
0.016 (0.001, 0.031), p=0.034 |
0.011 (-0.004, 0.026), p=0.152 |
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Change in BASDAI/ASDAS |
0.099 (0.065, 0.132), p<0.001 |
0.183 (0.122, 0.244), p<0.001 |
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Baseline mSASSS |
0.006 (0.003, 0.009), p<0.001 |
0.006 (0.003, 0.009), p<0.001 |
Conclusion: A decrease in MRI spinal inflammation predicts improvement in spinal mobility. This relationship is confounded by change in ASDAS but not by change in BASDAI. Spinal inflammation plays an important role in spinal mobility and therefore ASDAS (semi-objective) is a better means to follow (changes in) disease activity in AS than BASDAI (subjective). Therapeutic strategies specifically targeting MRI inflammation may contribute to improving spinal mobility of AS patients, independently of patient reported symptomatic improvement.
Disclosure:
P. Machado,
None;
R. Landewé,
None;
J. Braun,
None;
X. Baraliakos,
None;
K. G. A. Hermann,
None;
B. Hsu,
Centocor, Inc.,
3;
D. Baker,
Centocor, Inc.,
3;
D. van der Heijde,
None.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/in-ankylosing-spondylitis-a-decrease-in-mri-spinal-inflammation-predicts-improvement-in-spinal-mobility-independently-of-patient-reported-symptomatic-improvement/