Decipher the axial involvement of PsA patients for better diagnosis and predictive measures: The ASAS-PerSpA study

03 Feb 2023

In the 24th Asia-Pacific League of Associations for Rheumatology (APLAR) Congress, Professor Mitsumasa Kishimoto from the Kyorin University School of Medicine in Tokyo, Japan, presented the ancillary results of the ASAS-PerSpA study.1

With no consensus on defining the axial involvement of psoriatic arthritis (PsA), it is characterized by inflammatory involvement of the axial skeleton-sacroiliac joints and/or spine.1 ASAS-PerSpA was a cross-sectional study that determined the clinical profile of axial psoriatic arthritis (axPsA) as compared with axial spondyloarthritis (axSpA) in a worldwide setting, and identified the predictive factors associated with the development of axial involvement in PsA patients for rheumatologist diagnosis of axPsA vs. axSpA.1 The study recruited 3,684 participants aged ≥18 years who were diagnosed with PsA, axSpA, and peripheral spondyloarthritis (SpA) from 68 centers across 24 countries.1 Among these patients with axial involvement, 367 (12.2%) and 2,651 (87.8%) individuals were diagnosed with axPsA and axSpA, respectively.1

Patients with axSpA were predominantly male (65.8% vs. 53.5%) and younger at the study visit (42.1 vs. 50.0 years old), along with an elevated percentage of human leukocyte antigen B27 (HLA-B27)-positive (78.7% vs. 29.6%), inflammatory back pain (IBP) (94.9% vs. 87.6%) and uveitis (21.7% vs. 3.5%), compared with axPsA patient (p<0.001).1 Reversely, patients with axPsA showed a higher prevalence of peripheral arthritis (86.6% vs. 35.7%), psoriasis (88.3% vs. 7.0%), and the usage of conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) (92.4% vs. 51.3%) and biological DMARDs (bDMARDs) (71.7% vs. 59.8%).1 The treatment patterns were similar across all geographical regions, of which non-steroidal anti-inflammatory drugs (NSAIDs) were the most commonly prescribed drugs to both axPsA and axSpA patients (>91%).1 Notably, statistical differences in the csDMARDs use between axPsA and axSpA patients in Europe and North America (64% vs. 25%), and the Middle East and North Africa (53% vs. 31%) were significant, but not in Asia and Latin America.1 Besides, axPsA patients reported higher disease activity index than axSpA patients, including the Patient Global Assessment (PGA), the Ankylosing Spondylitis Disease Activity Score with C-reactive protein (ASDAS-CRP), the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the Bath Ankylosing Spondylitis Functional Index (BASFI), and the Assessment of Spondyloarthritis International Society Health Index (ASAS HI).1

According to a multivariable analysis, it was found that there were strong associations between diagnosis of axPsA and features, including age at diagnosis (OR=1.04; 95% CI: 1.02-1.05), peripheral arthritis (OR=7.32; 95% CI: 4.56-11.77), dactylitis (OR=2.82; 95% CI: 1.61-4.94), and psoriasis (OR=95.4; 95% CI: 59.1-153.9).1 Conversely, patients with axSpA were more prone to testing HLA-B27-positive (OR=0.26; 95% CI: 0.15-0.44), identifying the presence of sacroiliitis according to the modified New York (mNY) criteria in X-ray (OR=0.47; 95% CI: 0.31-0.78), sacroiliac joints according to the ASAS definition in magnetic resonance imaging (MRI) (OR=0.53; 95% CI: 0.29-0.93), and suffering IBP (OR=0.12; 95% CI: 0.03-0.47), and uveitis (OR=0.22; 95% CI: 0.10-0.47).1

The characteristics relating to axial involvement in 1,033 PsA patients were further analyzed to identify predictive factors for rheumatologist diagnosis, of which 367 (35.5%) patients suffered from axial involvement and 666 (64.5%) lacked the phenotype.1 Sociodemographic/pathogenic characteristics, including male gender (OR=1.68; 95% CI: 1.09-2.61), IBP (OR=84.34; 95% CI: 52.87-134.55), elevated C-reactive protein (CRP) (OR=2.87; 95% CI: 1.8-4.6) and the absence of psoriasis (OR=0.33; 95% CI: 0.15-0.72) were independently associated with axial involvement in PsA patients from the multivariable analysis.1

Findings of the ASAS-PerSpA study cohort concluded that to our knowledge, axPsA represents a unique phenotype with disease features overlapping between axSpA and pure peripheral PsA.1 Over one-third of PsA patients were diagnosed with axial involvement, having more affected patient-reported outcomes than axSpA patients.1 This study further revealed that male gender, elevated CRP, and the absence of psoriasis were strongly associated with axial involvement in PsA patients, which could potentially be the predictive markers for diagnostic purposes in the future.

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