Assessment of disease activity in psoriatic arthritis.

Psoriatic arthritis (PsA) historically has been assessed according to disease activity measures borrowed from rheumatoid arthritis. However, more disease activity measures specific to PsA have been developed. This development is appropriate, as the disease is not confined to the joints but has multiple manifestations, in addition to skin and joints. Assessments of disease activity are unique to each domain. Including different domains in composite measures increases the level of complexity. This review briefly discusses the available outcome measures, both within domains and as composite measures, and discusses likely future directions.