Background/Purpose: Psoriatic arthritis (PsA) develops in ~20-30% of psoriasis patients. However, early PsA diagnosis is challenging due to heterogeneous, subtle symptoms and overlap with psoriasis without arthritis (PsO). Even a brief diagnostic delay (~6 months) can lead to joint erosions and functional decline. We aimed to address this unmet need by identifying early clinical/imaging markers and developing a composite index for timely PsA detection.

Methods: We analyzed a retrospective case-control dataset (2014-2022) of 100 early PsA patients (≤2-year duration) and 100 psoriasis-only controls. All subjects underwent standardized clinical evaluation of tender/swollen joint counts (TJC, SJC), morning stiffness, enthesitis, and dactylitis, non-specific inflammatory biomarkers (ESR and CRP) along with musculoskeletal ultrasound and MRI imaging. A composite index (φAPs) was derived using multivariate logistic regression to integrate significant clinical and imaging predictors. Model performance (sensitivity, specificity, ROC area) was assessed and internally validated via bootstrap resampling.

Results: Early PsA patients demonstrated significantly elevated inflammatory activity compared to PsO controls. The mean TJC was 7.5±0.5 in early PsA vs 2.2±0.5 in PsO (p=0.0032), and the SJC was 4.5±0.3 vs 2.9±0.7 (p=0.0057), respectively. Morning stiffness duration was markedly longer in early PsA (37.7±5.5 minutes vs 10.2±4.5 minutes, p< 0.001). Enthesitis was present in 78% of PsA cases vs 31% in PsO (p=0.00023). Dactylitis affected 65.6% of early PsA patients, compared to 9% in PsO (p< 0.001), predominantly involving toes II–IV and fingers IV–V.Non-specific inflammatory biomarkers (ESR and CRP) were significantly elevated in early PsA: mean ESR was 37.8±2.4 mm/h vs 15.2±2.1 mm/h (p=0.0071); CRP was 36.25±2.23 mg/L vs 8.12±3.14 mg/L (p=0.0056). MRI detected tenosynovitis in 89.3% and early bone erosions in 40.4% of cases. Power Doppler ultrasonography identified active synovial proliferation in 91.7% and entheseal changes in key anatomical locations.The composite predictive model (φAPs), which integrates clinical and laboratory variables, demonstrated a sensitivity of 89% and specificity of 84% for early PsA identification. ROC curve analysis yielded an AUC of 0.91. Internal validation by 1,000 bootstrap replicates confirmed model robustness. In subgroup PsA analyses, φPsA values ≥2.3 correlated with confirmed early PsA in 92% of cases, while values < 1.8 excluded PsA in 95%. The most informative variables contributing to the model were dactylitis, enthesitis, and CRP elevation.

Conclusion: This composite clinical-imaging model greatly enhances early PsA recognition in psoriasis patients, enabling earlier intervention to prevent irreversible joint damage. By incorporating hallmark features like enthesitis and dactylitis, it helps clinicians distinguish incipient PsA from psoriasis alone at the earliest stages. External validation is underway to establish the φAPs index as a practical tool that improves clinical decision-making and patient outcomes.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/multidimensional-assessment-to-differentiate-early-psoriatic-arthritis-from-cutaneous-psoriasis/