Exploring the relationship between skin severity and PASDAS in psoriatic arthritis: a cross-sectional study in the BSR-PsA and GRACE cohorts.

Abstract

To explore the extent to which skin severity is reflected in the Psoriatic Arthritis Disease Activity Score (PASDAS). Cross-sectional baseline data from the British Society for Rheumatology PsA register (BSR-PsA) and the GRAPPA Composite Exercise (GRACE) dataset was included. The body surface area score (BSA) and the Dermatology Life Quality Index (DLQI) were used to assess skin disease activity. BSA was categorized as none (0%), mild (<3%), moderate (3-10%) and severe (>10%) skin involvement. DLQI was categorized as no (0-1), small (2-5), moderate (6-10), large (11-20) and extreme (21-30) effect on quality of life. Mean and standard deviation PASDAS scores, physician and patient global VAS scores were calculated for each category of skin severity by both BSA and DLQI. Within each cohort, two groups were created based on the severity of skin disease (BSA cut-off of 10). Propensity score matching was applied to match groups for musculoskeletal disease activity and differences between the groups were assessed. In both the BSR-PsA (N = 1126) and GRACE (N = 588) datasets, PASDAS, VAS physician global and VAS patient global scores increased with increasing skin scores. For the subjects grouped by severity of skin involvement, and matched for musculoskeletal activity, significant differences in PASDAS, physician global score and DLQI were observed for the BSR-PsA, and physician and patient global scores, DLQI and age for the GRACE dataset. These data suggest that psoriasis disease activity is represented in the composite PASDAS score, possibly through the global (patient and physician) VAS scores.