Criteria for psoriatic arthritis proposed by Vasey and Espinoza32
| Psoriatic arthritis is defined as criterion I plus one from either criterion II or III |
| Criterion I: Psoriatic skin or nail involvement |
| Criterion II: Peripheral pattern |
| (1) Pain and soft tissue swelling with or without limitation of movement of the distal interphalangeal joint for over four weeks |
| (2) Pain and soft tissue swelling with or without limitation of motion of the peripheral joints involved in an asymmetrical peripheral pattern for over four weeks. This includes a sausage digit |
| (3) Symmetrical peripheral arthritis for over four weeks, in the absence of rheumatoid factor or subcutaneous nodules |
| (4) Pencil in cup deformity, whittling of terminal phalanges, fluffy periostitis and bony ankylosis |
| Criterion III: Central pattern |
| (1) Spinal pain and stiffness with the restriction of motion present for over four weeks |
| (2) Grade 2 symmetric sacroiliitis according to the New York criteria |
| (3) Grade 3 or 4 unilateral sacroiliitis |