Table 1.

Classification criteria for psoriatic arthritis (CASPAR^*)⁶.

Established inflammatory musculoskeletal disease (joint, spine, or entheseal) with 3 or more of the following:
1. Psoriasis
(a) Current^†	Psoriatic skin or scalp disease present today as judged by a qualified health professional
(b) History	History of psoriasis that may be obtained from patient or qualified health professional
(c) Family history	History of psoriasis in a first or second-degree relative according to patient report
2. Nail changes	Typical psoriatic nail dystrophy including onycholysis, pitting, and hyperkeratosis observed on current examination
3. Negative test for RF	By any method except latex but preferably by ELISA or nephelometry, according to the local laboratory reference range
4. Dactylitis
(a) Current	Swelling of an entire digit
(b) History	History of dactylitis recorded by a qualified health professional
5. Radiological evidence of juxtaarticular new bone formation	Ill-defined ossification near joint margins (but excluding osteophyte formation) on plain radiographs of hand and foot

↵* The CASPAR criteria have specificity of 98.7% and sensitivity of 91.4%.
↵† Current psoriasis is assigned a score of 2; all other features are assigned a score of 1. CASPAR: ClASsification of Psoriatic ARthritis; RF: rheumatoid factor.