Functional Status in Early Axial Spondyloarthritis: The Role of Spinal Structural Damage

Structural damage in the spine and disease activity were both determinants of functional status and spine mobility in patients with early axial spondyloarthritis (axSpA), according to results of the German Spondyloarthritis Inception Cohort published in Rheumatology.

The German Spondyloarthritis Inception Cohort (GESPIC) study was conducted to investigate the functional relevance of the development of structural spine damage in patients with early axSpA. A total of 210 patients with early axSpA with symptom duration ≤10 years completed a 2-year clinical and radiographic follow-up. Researchers assessed structural damage using the modified Stroke AS Spine Score (mSASSS), functional status with the Bath Ankylosing Spondylitis Functional Index (BASFI), and spine mobility with the Bath Ankylosing Spondylitis Metrology Index (BASMI).

The results revealed an association between mSASSS and BASFI scores using both unstandardized (β= 0.05; 95% CI, 0.03-0.08) and standardized (β= 0.20; 95% CI, 0.11-0.59) regression analyses, after adjustments for disease activity parameters. Investigators also observed a stronger association between mSASSS and BASMI scores in unstandardized (β= 0.08; 95% CI, 0.05-0.11) and standardized analyses (β= 0.41; 95% CI, 0.25-0.57).

According to the investigators, these parameter estimates indicate that one mSASSS point is responsible for 0.05 points higher on the BASFI score and 0.08 points higher on the BASMI score, regardless of disease activity, presence of radiographic sacroilitis, and sex.

In addition, there was a significant association between clinical disease activity, as assessed by the BASDAI, and functional status (β= 0.79; 95% CI, 0.71-0.86) and spinal mobility (β= 0.22; 95% CI, 0.15-0.30).

“In patients with early axSpA, who typically have rather slow progression of structural damage in the spine, the disease activity seems to be the major determinant of functional status,” the authors concluded. “In contrast, only in the minority of patients with rapid radiographic spinal progression might structural damage become clinically relevant even early in the course of the disease.”

Reference

Poddubnyy D, Listing J, Haibel H, Knüppel S, Rudwaleit M, Sieper J. Functional relevance of radiographic spinal progression in axial spondyloarthritis: results from the GErman SPondyloarthritis Inception Cohort [published online January 24, 2018]. Rheumatology. doi:10.1093/rheumatology/kex475