Composite Measures for Routine Clinical Practice in Psoriatic Arthritis: Testing of Shortened Versions in a UK Multicenter Study

Objective: To test shortened versions of the psoriatic arthritis (PsA) composite measures for use in routine clinical practice.

Methods: Clinical and patient-reported outcome measures (PROMs) were assessed in patients with PsA at 3 consecutive follow-up visits in a UK multicenter observational study. Shortened versions of the Composite Psoriatic Arthritis Disease Activity Index (CPDAI) and Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) Composite Exercise (GRACE) measures were developed using PROMs and tested against the Disease Activity Score in 28 joints (DAS28), composite Disease Activity in Psoriatic Arthritis, and Routine Assessment of Patient Index Data (RAPID3). Discrimination between disease states and responsiveness were tested with the t-score, standardized response mean (SRM), and effect size (ES). Data were presented to members at the GRAPPA 2020 annual meeting and members voted on the recommended composite routine practice.

Results: The SRM for the GRACE, 3 visual analog scale (VAS), and 4VAS were 0.67, 0.77, and 0.63, respectively, and for CPDAI and shortened CPDAI (sCPDAI) were 0.54 and 0.55, respectively. Shortened versions of the GRACE increased the t-score from 7.8 to 8.7 (3VAS) and 9.0 (4VAS), but reduced the t-score in the CPDAI/sCPDAI from 6.8 and 6.1. The 3VAS and 4VAS had superior performance characteristics to the sCPDAI, DAS28, Disease Activity in Psoriatic Arthritis, and RAPID3 in all tests. Of the members, 60% agreed that the VAS scales contained enough information to assess disease and response to treatment, 53% recommended the 4VAS for use in routine care, and 26% the 3VAS, while leaving 21% undecided.

Conclusion: Shortening the GRACE to VAS scores alone enhances the ability to detect status and responsiveness and has the best performance characteristics of the tested composite measures. GRAPPA members recommend further testing of the 3VAS and 4VAS in observational and trial datasets.