A review of disease activity measures for psoriatic arthritis: what is the best approach?

The measuring tools for disease activity of rheumatoid arthritis have long been adapted for assessing the disease activity of psoriatic arthritis (PsA), particularly as regards peripheral arthritis. However, because of the multifactorial aspects and multiple domains of PsA, such as axial and peripheral joints, skin and nails, enthesitis and dactylitis, must also be considered when measuring activity. After the introduction of biologic agents, it became clear that more objective measuring tools were needed to assess the varied aspects of disease activity, as well as the effect of treatment. Collaborations among international groups of rheumatologists and dermatologists have helped define key or core domains of PsA that were recommended for inclusion in clinical trials and potentially clinical practice. Groups such as the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis have tried to develop and validate new outcome measures in PsA. Several new composite measures for specific PsA have been recently developed. The domains, instruments and traditional and new composite measures for PsA are reviewed herein.