Rheumatology (Oxford). 2026 Jul 27:keag309. doi: 10.1093/rheumatology/keag309. Online ahead of print.
ABSTRACT
OBJECTIVES: To compare the psychometric properties (inter-rater reliability, agreement, responsiveness, and measurement error) of the Psoriatic Arthritis Ratingen Score (PARS) and modified Sharp-van der Heijde (SVDH) methods using the Belgian Psoriatic Arthritis (BePas) cohort.
METHODS: Radiographs of hands and feet (baseline T0, follow-ups T1, T2) were independently scored by two blinded readers using SVDH (max 528) and PARS (max 360). Statistical analyses included Intraclass Correlation Coefficient (ICC), Bland-Altman analysis, Standardized Response Mean (SRM), and Smallest Detectable Change (SDC).
RESULTS: Both methods detected positive mean change, primarily between T0 and T1. Inter-rater reliability for absolute scores was high for both (ICC >0.865; baseline ICC: PARS 0.906, SVDH 0.888). For cumulative change scores (ΔT2-T0), inter-rater reliability was low and very similar for both methods (ICC=0.483 for SVDH and 0.485 for PARS). Both methods showed moderate responsiveness over the cumulative interval (two-reader average SRM: PARS 0.571, SVDH 0.531). For both methods and both readers, mean cumulative change scores were smaller than the corresponding SDC values (PARS: 2.8-3.7% of maximum score; SVDH: 2.8-4.1%), indicating that average progression fell below the threshold of reliable individual-level detection. Bland-Altman analysis showed slightly narrower absolute limits of agreement for PARS in selected comparisons, whereas SVDH showed narrower relative limits after normalization to the maximum possible score.
CONCLUSIONS: SVDH and PARS showed broadly comparable psychometric performance for PsA damage assessment. Both methods were robust for cross-sectional scoring but showed important limitations in reliably detecting cumulative change in this low-progression cohort. Neither method demonstrated clear superiority.
PMID:42507901 | DOI:10.1093/rheumatology/keag309
