Background/Purpose:

Relapsing polychondritis (RP) is a rare multi-systemic disorder characterized by recurrent, destructive, inflammatory lesions of the auricular, nasal, and laryngo-tracheo-bronchial cartilages. Additional clinical features include ocular inflammation, audio-vestibular impairment, vasculitis, skin involvement, valvular insufficiency, and non-erosive arthritis. The rarity of the disease makes it difficult to provide a standardized approach for treatment and follow-up of RP patients, and there is no consensus agreement on any outcome measures in this disease. Here, we describe the development of a score for assessing disease activity in RP, the Relapsing Polychondritis Disease Activity Index (RPDAI).

Methods: This study reflects a multi-center, international and interdisciplinary collaboration of experts involved in the management of RP. Selection and definition of items for disease activity were established by consensus between 27 experts during a 4-round internet-based Delphi survey. Then, twenty-six experts assessed the Physician’s Global Assessment (PGA) of disease activity of 43 test cases on a 0-100 scale. The weight of each item was estimated by multivariate regression models with generalized estimating equation, using PGA as the dependent variable.

Results:

Experts decided in consensus that the RPDAI should consider the 28-day period before each scoring. Twenty-seven items were selected using the Delphi survey and a glossary defining each item was derived by consensus. Then, item weighting was performed by 26 experts, who assessed the Physician’s Global Assessment (PGA) of disease activity of 43 test cases on a 0-100 scale. Inter-rater reliability assessed by the intra-class correlation coefficient for these PGA ratings was 0.51 (CI95%: 0.41-0.64). Multivariate analysis revealed that the individual weigh of items ranged from 1 to 24. The final RPDAI score therefore comprised 27 items with a maximum theoretical score of 265. Correlation between the RPDAI scores calculated for all test cases based on the weights derived from the final multivariate model, and the PGA of these cases was good (r=0.56, p<0.0001).

Conclusion:

We have developed a consensus scoring system to measure disease activity in relapsing polychondritis (see www.RPDAI.org for online scoring). We believe this tool will be valuable for improving the care of patients with this rare disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-relapsing-polychondritis-disease-activity-index-international-development-and-initial-validation-of-the-first-disease-activity-score-for-relapsing-polychondritis/