ASSESSMENT OF PSORIATIC ARTHRITIS (PSA)

B.A.C. DijkmansRheumatology, VU medical centre, Amsterdam, NetherlandsPsA is defined as a disorder characterized by inflammation of the joints associated with psoriasis. Because of the heterogeneous character, the defining of the outcome measures has been a challenge. At present, such measures have largely been adapted from other rheumatic diseases. The following items will be highlighted: 1.aspects of heterogenicity of PsA; 2. clinical assessment of PsA; 3. imaging assessment of PsA. The present abstract is to a great extent based on the OMERACT7 workshop. Previously, inflammatory arthritis in combination with psoriasis was considered to represent rheumatoid arthritis occurring coincidentally with psoriasis. Wright described the frequent involvement of distal interphalangeal (DIP) joints and proximal interphalangeal (PIP) joints of the toes, and a mutilating arthritis. The American College of Rheumatology has adopted PsA as a distinct clinical entity. Unfortunately, validated criteria such as those developed for RA do not yet exist for PsA.For decades the diagnostic criteria of Moll and Wright have been used in current studies. Five subgroups of PsA are described: DIP joints only, asymmetrical oligoarthritis, polyarthritis, spondylitis and arthritis mutilans. At present, there is no consensus on how to define PsA in the best possible way. Therefore, it is necessary to develop new, internationally agreed criteria based on patient data. The classification of a PsA (CASPAR) study should provide the way forward in the classification of PsA. The measures used to assess joint disease include: 1. ACR Response Criteria developed for RA; 2. The PsA Response Criteria (PsARC), developed by Dan Clegg; 3. The Disease Activity Score (DAS).ACR Response Criteria and PsARC instruments were used either as a primary or as a secondary response measure in all of the recent randomized trials in PsA. The placebo response in these trials was low both for ACR 20 and for the PsARC. In the anti-tumor necrosis factor trials, patients demonstrated high response rates when using both instruments. The DAS has the advantage that it can track both the disease activity and the response to change. However, a current limitation of the DAS is that DIP joints are excluded, and the inclusion of this criterion requires revalidation.Since psoriasis is a major component in PsA, it is important to assess both skin and joints. Two approaches for endpoints are being used: one is subjective and the other is objective. For the subjective endpoints the physician and/or patient is asked to give a global score on the Physicians or Patients Global Assessment (PGA or PtGA). More specific tools include the Psoriasis Severity Index (PASI), the Lattice System Physician Global Assessment and the National Psoriasis Foundation Psoriasis Score (NPF-PS).A limitation of the PASI is that induration, supposedly the most sensitive aspect, is not carefully defined. The Lattice Assessment was developed in order to qualitatively assess elements of each plaque.The NPF-PS is a composite assessment of investigator and patient characteristics developed as an answer to the US Food and Drug Administration's criticism of PASI and to include skin involvement of psoriasis into a system using ACR and PsA response criteria assessment of joint disease. This instrument is based on characteristics that are considered to be the most sensitive (thickness of two target lesions and a change in body surface area, from baseline in assessing psoriasis, and it was also created to provide better cross-study comparisons versus the current instruments. In general the focus of imaging is on the changes in peripheral joints in patients with PsA. With regard to the assessment of peripheral joints several scoring methods have been proposed, based on existing scoring systems for RA and adapted for use in PsA. Radiological progression in peripheral joints of PsA patients has been assessed in Toronto by a modification of the Steinbrocker technique. In this method the Toronto group have scored all the joints of the hands, all MTPs and the IP joints of the big toe. In addition to the original Sharp scoring method for RA a number of radiographic features seen in PsA were scored: amongst others shaft periostitis. The Sharp/van der Heijde modifying scoring method for PsA is based on the Sharp/van der Heijde method in RA. The proposed adapted scoring method for PsA is a detailed scoring method evaluating erosions, joint space narrowing, (sub) luxation, ankylosis, gross osteolysis, and pencil in cup phenomena. Moreover, the DIPs of the hands were assessed. A further evaluation of the various, radiologic methods is needed. A working group has been formed to accomplish this task and further progress will be presented at OMERACT 8.References: 1. Outcome measures in Psoriatic Arthritis. Gladman DD et al, J Rheumatol. 2005;32:2262-9.2. Psoriatic Arthritis Imaging: A review of scoring methods. Van der Heijde D, Ann Rheum. Dis 64;March 2005,suppl 2:ii 61-4.Citation: Ann Rheum Dis, volume 65, supplement II, year 2006, page 32Session: PsA: best practice in 2006