Factors explaining the discrepancy between physician and patient global assessment of joint and skin disease activity in psoriatic arthritis patients.

OBJECTIVE: To assess the extent and determinants of discordance in scoring between patient global assessment (PtGA) and physician global assessment (PhGA) in patients with psoriatic arthritis (PsA).
METHODS: A cross-sectional and longitudinal analysis of data was conducted in patients attending a large PsA clinic. The difference between PtGA and PhGA (each measured on a scale of 0-10, with 0 indicating best status and 10 indicating worst status) reflected the discrepancy between the PtGA and PhGA of joint and skin activity and could take values from -10 (higher rating of disease activity by the patient) to 10 (higher rating of disease activity by the physician). Multivariate regression identified variables that contributed significantly to each of the outcomes. The proportion of variability of each outcome explained by each predictor was expressed by the partial R(2) .
RESULTS: A total of 565 patients were included in the analysis. Patients tended to score their disease worse than their physicians, with greater discordance for the joints than for the skin (mean ± SD 1.68 ± 2.41 PtGA-PhGA difference for joints, and 0.77 ± 2.66 for skin). Fatigue accounted for 21% of the variation in the difference between PtGA and PhGA for joints. Pain (Rpartial2 = 9%) and disability by Short Form 36 health survey (Rpartial2 = 1.2%) were also important factors, each of which led to higher patient rating; whereas increased tender joint count (Rpartial2 = 16%) and swollen joint count (Rpartial2 = 1.4%) resulted in a higher physician rating of arthritis.
CONCLUSION: Fatigue, pain, disability, and tender and swollen joint counts were the most important factors contributing to discrepancy between patient and physician assessment of joint activity.