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

Abstract

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.

Keywords::

• assessment
• composite score
• disease activity
• domain
• outcome measure
• psoriatic arthritis

Financial & competing interests disclosure

A Kavanaugh has conducted clinical research sponsored by Amgen, AbbVie, UCB, Roche, Celgene, Pfizer, BMS, and Janssen. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Excellent biological agent efficacy in psoriatic arthritis (PsA) leads to increased recognition of skin, enthesitis, dactylitis and arthritis as important outcomes in clinical trials.

• Several composite measures, such as the American College of Rheumatology response, the European League Against Rheumatism response, Disease Activity Score and Disease Activity in Psoriatic Arthritis (DAPSA), were borrowed from other diseases, such as RA or reactive arthritis.

• Psoriatic Arthritis Response Criteria, Psoriatic Arthritis Joint Activity Index, Composite Psoriatic Arthritis Disease Activity Index, Psoriatic Arthritis Disease Activity score (PASDAS) and Arithmetic Mean of Desirability Function (AMDF)/GRAppa Composite Exercise (GRACE) index are composite measures developed specifically for PsA.

• There have been a number of attempts to develop and validate new outcome measures in PsA.

• Groups such as the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) conducted a large observational study, the GRACE project and developed new PsA-specific composite outcome measures, PASDAS and the GRACE index.

• The concept of minimal disease activity was applied to PsA, and the cutoff for composite measures of disease activity was determined at the GRAPPA meeting.

• Highly sensitive imaging tools will likely be utilized in order to help assess disease activity of several domains of PsA in the future.

• To date, there is no single, acceptable gold standard measuring tool for PsA disease activity.