Development of composite measures for psoriatic arthritis: a report from the GRAPPA 2010 annual meeting.

Composite disease outcome measures have been used in rheumatology for some time, but a disease-specific composite measure for psoriatic arthritis (PsA) has not yet been validated. Currently, instruments developed for use in rheumatoid arthritis are employed in PsA and include the American College of Rheumatology response criteria (ACR20, 50, and 70) and the Disease Activity Score for 28 and 44 joints (DAS28 and DAS44); however, these instruments do not cover the full spectrum of psoriatic disease. A composite measure is one way of incorporating an assessment of all relevant clinical outcomes into one single measure. By definition, it incorporates several dimensions of disease status, often by combining these different domains into a single score, which in the case of PsA includes joints, skin, entheses, dactylitis, and axial disease. New indices that combine these diverse clinical manifestations of PsA are under development and, in some cases, in the validation phase. The Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) established the GRAPPA Composite Exercise (GRACE) project to compare existing and emerging composite measures and to develop a new index. At the GRAPPA 2010 meeting, initial results from this project were presented, and existing and new candidate measures were compared.