Longitudinal Association Between Trabecular Bone Loss and Disease Activity in Axial Spondyloarthritis: A 4-year Prospective Study

Abstract

Objective.To investigate whether trabecular bone loss is longitudinally associated with disease activity measures in patientswith axial spondyloarthritis (axSpA).Methods.Data from patients enrolled in the Incheon Saint Mary’s axSpA prospective observational cohort were evaluated. Trabecular bone loss was assessed using the trabecular bone score (TBS). The relationship between TBS and disease activity measures [Ankylosing Spondylitis Disease Activity Score (ASDAS), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP)] was investigated using generalized estimating equation (GEE) models.Results.Four-year followup data from 240 patients (80% males, mean age 37 ± 12 yrs) were evaluated. At baseline, higher disease activity according to ASDAS-ESR and ASDAS-CRP showed a trend toward lower TBS (p = 0.003 and p = 0.016, respectively). Univariate GEE analyses showed a significant association between TBS and disease activity measures over time, with the exception of BASDAI. Univariate analysis showed a longitudinal association between TBS and age, smoking, and spinal structural damage. In multivariate GEE analysis, ASDAS-ESR, ASDAS-CRP, ESR, and CRP were longitudinally associated with TBS after adjustment for confounding factors. ASDAS scores and inflammatory markers were longitudinally associated with TBS in patients with ankylosing spondylitis (AS; 79%), but not in patients with nonradiographic axSpA (nr-axSpA). BASDAI scores showed no relationship with TBS in either the AS or nr-axSpA groups.Conclusion.Trabecular bone loss in patients with axSpA, assessed using the TBS, showed a longitudinal association with ASDAS scores and inflammatory markers.