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ABSTRACT: The diagnosis of psoriatic arthritis (PsA) often is missed, partly because patients may present with inflammatory spinal pain, tendinitis, enthesitis, or dactylitis rather than a "true arthritis." If PsA is not identified early and managed appropriately, progressive joint damage with deformities and disability may result. Several classification criteria have been proposed, but none have been widely accepted or validated. Given issues with earlier criteria, the ClASsification criteria for Psoriatic ARthritis (CASPAR) study was started to develop a new set of validated classification criteria. 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.
Psoriatic arthritis (PsA), a chronic inflammatory arthritis, usually is seronegative for rheumatoid factor (RF) and is associated with cutaneous psoriasis. Initially thought to be rheumatoid arthritis (RA) occurring simultaneously with psoriasis, PsA was not recognized as a distinct clinical entity by the American College of Rheumatology (ACR) until 1964.1
Although between 5% and 30% of patients who have psoriasis are reported to have accompanying PsA,2 the diagnosis of PsA often is missed in primary care physicians' and dermatologists' offices. A major reason is that patients with PsA may present with inflammatory spinal pain, tendinitis, enthesitis, or dactylitis rather than a "true arthritis."
If PsA is not identified early and managed appropriately, progressive joint damage with deformities and disability may result. The quality of life in patients who have PsA is reported to be much worse than in those who have only psoriasis.3 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....