Undifferentiated arthritis

If PsA is not identified early and managed appropriately, progressive joint damage with deformities and disability may result. Several classification criteria have undifferentiated arthritis proposed, but none have been widely accepted or validated.

The CASPAR criteria permit the diagnosis of PsA in spite of low rheumatoid factor positivity. They offer classification criteria that are simple and easy to use with a high degree of specificity and good sensitivity. PsA often is missed in primary care physicians’ and dermatologists’ offices. The quality of life in patients who have PsA is reported to be much worse than in those who have only psoriasis. The advent of effective new therapies, such as biologic agents, has made widely accepted and validated classification criteria imperative for PsA research trials to be meaningful.

This is the fifth article in a series on new or modified classification and diagnostic criteria for various rheumatologic conditions. ACR diagnostic criteria for fibromyalgia syndrome and their modification as survey criteria. In this article, we describe the classification criteria for PsA. The Moll and Wright Classification Criteria for PsA, proposed in 1973, are the oldest and best known.