Psoriatic arthritis – definition and classification criteria Philip Helliwell Senior Lecturer in Rheumatology University of Leeds

Psoriatic arthritis Wright V Annals of Rheumatic Diseases 1961;20:

Too sensitive? Too specific?

Psoriatic arthritis – key individual features Psoriasis Symmetry Rheumatoid factor

Psoriasis May be hidden May be coming May have gone May be in family May be misdiagnosed

Symmetry in early and late psoriatic and rheumatoid arthritis

Joint frequency by disease

Psoriatic arthritis - the significance of rheumatoid factor Moll and Wright excluded (usually) Gladman (and others) included ( up to 15%) Not unreasonable to allow RF as may just reflect a chronic inflammatory state Need to: –Reliably exclude the seronegative rheumatoid arthritis –Reliably include the seropositive psoriatic arthritis

Rheumatoid factor Could we make this test more specific? –Rheumatoid factor isotypes Or use other tests? –Anti-perinuclear factor –Anti-CCP antibodies

Summary of CART analysis Variables entered Splitters selected by CART SensSpec All dataCurrent psoriasis All data excluding psoriasis RF, dactylitis All except psoriasis and RF Dactylitis, nodules, symmetry, chest wall pain, juxta-articular new bone,  4 mcp joints, sacroiliitis, PVO, ankylosis, entheseal new bone, chest wall pain, clinical spondylitis

Psoriatic arthritis –one disease or more? Large joint mono/oligoarthritis Entheseal disease (including spinal disease) SAPHO/CRMO DiP and mutilans Symmetrical polyarthritis + Ps = RA?

Psoriatic arthritis – does it exist? Cats believed psoriasis merely modifies inflammatory response Immunogenetic data not all that convincing Inflammatory response has an array of common pathways

Psoriatic arthritis – why bother? Same NSAIDs Same DMARDs Same biologics BUT… Nosology Good and bad prognostic disease Treatment outcome Treatment indications

Impairment, disability and quality of life in RA and PsA

Disability and quality of life in RA and psoriatic arthritis according to severity of arthritis

Validation of classification criteria for psoriatic arthritis 700 patients with psoriatic arthritis 700 controls with inflammatory arthritis and inflammatory OA Standardised proforma Clinical and historic data Radiographic data Genetic data Quality control A prospective multi-centre international case control study

Analysis by: –Conditional logistic regression –Latent class analysis –Classification and regression trees International study All major ‘players’ Consensus criteria Based on sound methodology Validation of classification criteria for psoriatic arthritis RESULTS AVAILABLE IN

What will CASPAR do? Enable us all to use the same criteria Distinguish between seronegative rheumatoid arthritis and psoriatic arthritis Facilitate studies of –natural history –Treatment –immunogenetics

Psoriatic arthritis Is a distinctive disorder New criteria need to encapsulate this while not being exclusive A distinctive (and preferably pathogenic) biologic marker would help