Composite disease activity and responder indices for psoriatic arthritis: a report from the GRAPPA 2013 meeting on development of cutoffs for both disease activity states and response.

OBJECTIVE: There are several new composite indices for assessing disease activity in psoriatic arthritis (PsA). Each may function as a disease state variable and a responder index. The aim of our study was to determine cutoffs for disease activity and response.

METHODS: Data from the Group for GRAPPA Composite Exercise (GRACE) study were used to develop cutoffs using a number of different approaches. Voting on choice of cutoff was undertaken at the 2013 GRAPPA Annual Meeting in Toronto, Ontario, Canada.

RESULTS: After voting, results for cutoffs for low/high disease activity for the Psoriatic ArthritiS Disease Activity Score (PASDAS), GRAppa Composite scorE (GRACE index), and Composite Psoriatic Disease Activity Index (CPDAI), respectively, were 3.2/5.4, 2.3/4.7, and 4/8. The measurement error for each composite score was estimated at 0.8, 1, and 2 for PASDAS, GRACE, and CPDAI, respectively.

CONCLUSION: Response criteria for the new composite indices have been developed. These now require further validation and testing in other datasets.