Table 1

 Criteria for psoriatic arthritis (PsA) proposed by Bennett31

    Clinically apparent psoriasis (skin or nails)
    Pain and soft tissue swelling and/or limitation of motion in at least one joint observed by a physician for six weeks or longer
    Pain and soft tissue swelling and/or limitation of motion in one or more other joints observed by a physician
    Presence of an inflammatory arthritis in a distal interphalangeal joint. Specific exclusions: Bouchard’s or Heberden’s nodes
    Presence of “sausage” fingers or toes
    An asymmetrical distribution of arthritis in the hands and feet
    Absence of subcutaneous nodules
    A negative test for rheumatoid factor in the serum
    An inflammatory synovial fluid with a normal or increased C3 or C4 level and an absence of infection (including acid fast bacilli) and crystals of monosodium urate or pyrophosphate
    A synovial biopsy showing hypertrophy of the synovial lining with a predominantly mononuclear cell infiltration and an absence of granuloma or tumour
    Peripheral radiographs showing erosive arthritis of small joints with a relative lack of osteoporosis. Specific exclusion: erosive osteoarthritis
    Axial radiographs showing any of the following: sacroiliitis, syndesmophytes, paravertebral ossification
Definite PsA: mandatory plus six supportive
Probable PsA: mandatory plus four supportive
Possible PsA: mandatory plus two supportive