Background/Purpose: Relapsing polychondritis (RP) is a rare systemic inflammatory disorder of cartilage that lacks validated disease activity measures. Physician global assessment (PhGA) is a measure of disease activity frequently used in a variety of rheumatologic diseases to track treatment response and categorize disease states. PhGA has not been studied specifically in a cohort of patients with RP. The objective was to characterize the reliability and utility of PhGA for RP.

Methods: Adult patients in an ongoing observational cohort who meet existing diagnostic criteria for RP underwent a standardized comprehensive evaluation at approximately 6-month intervals. PhGA was scored by consensus of 3 raters on a scale of 0 (no clinical activity) to 10 (maximum disease activity) at each study visit. Ratings were considered discordant if any two ratings differed by three or more points. Change in immunosuppressive treatment between consecutive visits was recorded as increased, decreased or unchanged. Intraclass correlation coefficients (ICC) (2, 1), Spearman’s correlation, Fisher’s exact test and Wilcoxon signed rank were used to characterize the reliability and utility of PhGA as a measure of disease activity.

Results: 78 patients were evaluated over visits. The ICC for the ratings by the 3 raters was 0.79 (95 % confidence interval:0.73-0.84), indicating good reliability. For 6 out of 164 visits (3.7%) the ratings by the 3 raters were discordant. After adjudicating the discordant ratings, the assigned PhGA ranged from 0-7 with a median of 3 (interquartile range 2-3). PhGA was 0 at 4 visits (2%), 1 or 2 at 76 visits (46%), 3 or 4 at 63 visits (38%), and more 5 or more at 22 visits (13%). PhGA was weakly correlated with CRP (r= 0.30, P< 0.001) but not with ESR (r=0.13, P=0.10). Between the baseline and the first follow-up visit there was decrease in PhGA from median of 3 (interquartile range 2-5) to median of 2 (interquartile range of 1-3) (P< 0.001). There was no further change in PhGA over subsequent consecutive follow-up visits. Between consecutive visits in which there was an increase in immunosuppressive treatment, the median PhGA decreased from 3 (interquartile range 2-4) to 2 (interquartile range 2-3) (P< 0.001) but rarely went to 0. Between consecutive visits in which there was no change or a decrease in treatment, there were no corresponding changes in PhGA.  

Conclusion: PhGA is a reliable measure to quantify disease activity and monitor treatment response in RP. Even with treatment, few patients with RP have a PhGA of 0, suggesting that a state of no clinical activity is difficult to achieve or that damage may be masquerading as low disease activity in some patients. These data provide insight into the burden of disease activity in RP and highlight a need for improved treatments.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validation-of-physician-global-assessment-as-an-outcome-measure-in-relapsing-polychondritis/