Criteria for psoriatic arthritis (PsA) proposed by Bennett31
| Mandatory |
| 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 |
| Supportive |
| 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 |