Disclosures: Carvalho reports no relevant financial disclosures. Co-author Pedro M. Machado, MD, PhD, of University College, in London, reports consulting or speaking fees from Abbvie, Bristol Myers Squibb, Celgene, Eli Lilly & Co., Janssen, MSD, Novartis, Pfizer, Roche and UCB.
November 30, 2020
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Disease activity tops 'key drivers of disability' in axial SpA

Disclosures: Carvalho reports no relevant financial disclosures. Co-author Pedro M. Machado, MD, PhD, of University College, in London, reports consulting or speaking fees from Abbvie, Bristol Myers Squibb, Celgene, Eli Lilly & Co., Janssen, MSD, Novartis, Pfizer, Roche and UCB.
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Among patients with axial spondyloarthritis, disease activity surpassed other "key drivers" such as enthesitis, gender and spinal mobility in explaining disability, according to data published in Arthritis Care & Research.

“In a proposed stratified model for health outcomes in axSpA, disability was showed to be hierarchically inferior to health-related quality of life, and hierarchically superior to disease activity and spinal mobility,” Pedro D. Carvalho, MD, of the Algarve University Hospital Center, in Faro, Portugal, and colleagues wrote. “The association between disability and impairment of spinal mobility as well as with disease activity has been reported mainly is ankylosing spondylitis (AS) patients with established disease. Furthermore, longitudinal studies are scarce.”

Among patients with axial SpA, disease activity contributes longitudinally to, and is hierarchically superior to all other variables in explaining, disability, according to findings. Source: Adobe Stock

“The Ankylosing Spondylitis Disease Activity Score-C-reactive protein (ASDAS-CRP) has been progressively replacing the Bath Ankylosing Spondylitis Disease Activity Score (BASDAI) as the main disease activity measure to assess patients with axSpA, both in the research context as well as in clinical practice,” they added. “However, further evidence is needed to demonstrate its meaningfulness regarding the longitudinal relationship with disability, particularly in the early axSpA subgroup.”

To analyze the long-term link between disease activity and disability among patients with axial SpA, Carvalho and colleagues analyzed data from the Devenir des Spondylarthropathies Indifferénciées Récentes (DESIR) cohort. According to the researchers, DESIR is a prospective observational study of patients with recent onset — less than 3 years — inflammatory back pain suggestive of axSpA. Focusing on the first 5 years of follow-up, the researchers included data from 644 patients and 5,152 visits in their analysis.

Carvalho and colleagues built multivariable models to study the association between the Ankylosing Spondylitis Health Assessment Questionnaire (HAQ‐AS) and the Ankylosing Spondylitis Disease Activity Score C‐reactive protein (ASDAS‐CRP) domains, adjusting for potential confounders. In addition, they performed a hierarchical multivariable analysis, using the Chi‐square Automatic Interaction Detector (CHAID) method, to determine how variables best cluster to explain HAQ‐AS.

According to the researchers, HAQ‐AS was longitudinally, independently and positively associated with ASDAS‐CRP (adjusted B = 0.205; 95% CI, 0.187-0.222), enthesitis score (adjusted B = 0.011; 95% CI, 0.008-0.015), Bath Ankylosing Spondylitis Metrology Index (adjusted B = 0.087; 95% CI, 0.069-0.105) and female gender (adjusted B = 0.172; 95% CI, 0.12-0.225). In addition, the CHAID decision tree revealed ASDAS‐CRP as the first variable with discriminative power on HAQ‐AS.

“We have shown that disease activity contributes longitudinally to disability, and that it is hierarchically superior to any other variables or disease domains, in the context of an early axSpA cohort with minimal structural damage,” Carvalho and colleagues wrote. “Enthesitis, gender and spinal mobility are also key drivers of disability in early axSpA. ASDAS-CRP, a composite index used to measure disease activity in axSpA, also reflects the level of disability, and its cut-offs are able to discriminate between different profiles of disability in early axSpA, reinforcing the validity of the ASDAS-CRP disease activity cut-offs.”