Spinal radiographic progression in axial spondyloarthritis and the impact of classification as nonradiographic versus radiographic disease: Data from the Swiss Clinical Quality Management cohort.

Burkhard Möller,Xenofon Baraliakos,Adrian Ciurea,Pascal Zufferey,Robert Landewé,Pascale Exer,Désirée van der Heijde,Raphael Micheroli,Monika Hebeisen,Michael J. Nissen,Kristina Bürki,Manouk de Hooge,Almut Scherer

doi:10.1371/journal.pone.0230268

Abstract

ObjectiveTo investigate whether spinal radiographic progression relates to structural damage at the sacroiliac level in axial spondyloarthritis (axSpA).MethodsPatients classified as nonradiographic (nr-) and radiographic (r-) axSpA in the Swiss Clinical Quality Management cohort with radiographs performed every 2 years, scored according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS), were included. The relationship between classification status and spinal progression during 2 years was investigated using binomial generalized estimating equations models with adjustment for sex, ankylosing spondylitis disease activity score (ASDAS) and tumour necrosis factor inhibitor treatment. Baseline spinal damage was considered an intermediate variable and included in sensitivity analyses.ResultsIn total, 88 nr-axSpA and 418 r-axSpA patients contributed to data for 725 radiographic intervals. R-axSpA patients were more frequently male, had a longer disease duration and higher structural damage at baseline. Mean (SD) mSASSS change over 2 years was 0.16 (0.62) units in nr-axSpA and 0.92 (2.78) units in r-axSpA, p = 0.01. Nr-axSpA was associated with a significantly lower progression in 2 years (defined as an increase in ≥2 mSASSS units) in adjusted analyses (OR 0.33, 95%CI 0.13; 0.83), confirmed with progression defined as the formation of ≥1 syndesmophyte. Mediation analyses revealed that sacroiliitis exerted its effect on spinal progression indirectly by being associated with the appearance of a first syndesmophyte (OR 0.09, 95%CI 0.02; 0.36 for nr-axSpA vs r-axSpA). Baseline syndesmophytes were predictors of further progression.ConclusionSpinal structural damage is mainly restricted to patients with r-axSpA, leading to relevant prognostic and therapeutic implications.

Highlights

Functional limitation of the spine in axial spondyloarthritis is the consequence of both disease activity and accumulated spinal structural damage [1, 2]
88 nr-axial spondyloarthritis (axSpA) and 418 r-axSpA patients contributed to data for 725 radiographic intervals
Spinal structural damage is mainly restricted to patients with r-axSpA, leading to relevant prognostic and therapeutic implications

Summary

Introduction

Functional limitation of the spine in axial spondyloarthritis (axSpA) is the consequence of both disease activity and accumulated spinal structural damage [1, 2]. Very limited data on spinal radiographic progression exists for the nonradiographic disease form (nr-axSpA) [4, 10], an entity differentiated from r-axSpA by the absence of definite sacroiliac damage on radiographs [15, 16], according to the modified New York criteria (mNYc) [5], but presenting from a clinical point of view, a burden of disease comparable to r-axSpA despite lower spinal structural damage [17,18,19,20,21,22,23]. An indirect association would occur if—from the perspective of localization—osteoproliferation would primarily affect the sacroiliac joints and would only later affect the spine In this case, syndesmophytes would predominantly occur in patients already presenting with sacroiliac damage. This does not correspond, to the current radiographic and histological data available, as erosive damage followed by putatively reparative osteoproliferation is occurring at both locations of the axial skeleton [25, 26]

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Conclusion