The CASPAR classification criteria and response to TNF blockade in Rheumatologists’ practice: A large observational cohort study

Burkhard Möller, Almut Scherer, Jean Dudler, Bettina Weiss, Nikhil Yawalkar, Peter M. Villiger, on behalf of the Swiss Clinical Quality Management Program for Rheumatic Diseases.

Background/Purpose: Background/Purpose: Definition of the CASPAR classification criteria and TNF blocker therapy were milestones in the area of psoriatic arthritis (PsA). We aimed to identify the ‘CASPAR-positive’ patients in a large patient population, and to compare the results of TNF blockade in ‘CASPAR-positive’ and in ‘CASPAR-negative’ patients with background psoriasis.

Methods: Patients in the SCQM database had a primary diagnosis of PsA on an individual decision by the treating board certified rheumatologist. Classification relevant data were in addition requested at baseline and at annual intervals. Disease activity was displayed by the physician global (PhG), patient global (PG) and pain assessment, the 66 swollen (SJC) and 68 tender joint counts (TJC), the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) serum concentrations, and numeric rating scales for skin and nail involvement.

Results: 543 female and 601 male patients were included with PsA diagnosis. Only 183 (16%) of them came from academic centers, but 231 (20%) from other hospitals and 690 (60.3%) from practice based rheumatologists. A current or a history of arthritis (81%), enthesitis (46%) or dactylitis (49.5%) was reported either alone or in combination. Axial involvement (38%) without further specification and inflammatory back pain (12%) were less frequent. Current skin psoriasis (71%) at inclusion was mild or moderate in 52% and/or obtained from the patient history in 70%. Nail involvement was registered in 9%, a positive patient’s family history in  22%, positive rheumatoid factor testing in 1.8%, and PsA-typical juxta-articular osteoproliferation in 13.5% of the patients. The proportion of CASPAR-positive SCQM-PsA patients (n=625 or 54.6%) was equally distributed among the university centers and practices.

361 CASPAR-positive and 239 CASPAR-negative PsA patients were started on a TNF blocker: 223 on adalimumab (104 with background MTX), 180 on etanercept (79 plus MTX), 73 on infliximab (45 plus MTX) and 24 patients on golimumab (8 plus MTX). 302 CASPAR-positive and 188 CASPAR-negative PsA patients had at least one follow-up visit one year later, when the following parameters had improved: SJC from mean 4.5 (SD: 6.1) to 2.0 (SD: 4.6), TJC from 8.1 (SD: 11.5) to 4.4 (SD: 8.5), CRP from 11.4 (SD: 16.4) to 6.3 mg per liter (SD: 6.4), PhG from 4.2 (SD: 2.4) to 2.0 (SD: 1.9), PG from 5.1 (SD: 2.9) to 3.4 (SD: 2.7) and pain from 5.0 (SD: 2.8) to 3.5 (SD: 2.8). There were no differences in these disease activity measures between patients satisfying the CASPAR criteria and the ‘CASPAR-negative’ patients, neither at baseline nor at 1-year post TNF blocker initiation.

Conclusion: This study confirms that the CASPAR classification criteria could be useful in practice for affirming PsA diagnosis, but they should not stringently be used as an exclusive selection criterion for anti-TNF therapy in patients with background psoriasis.