Objectives: Psoriatic arthritis (PsA) has been defined as a systemic, chronic, inflammatory arthritis, usually seronegative for rheumatoid factor (RF), associated with cutaneous psoriasis. The exact prevalence of PsA is unknown and its estimation has been difficult, partly due to the lack of a widely accepted classification criteria. Agreed and validated criteria will facilitate comparison between centres and different countries in the areas of epidemiology, outcome studies and therapeutic trials. A number of classification criteria have been published by Moll & Wright (M & W), Bennett's, Vasey and Espinoza (V & E), Fournié's, European Spondyloarthropathy Study Group (ESSG), McGonagle, Gladman and most recently, the CASPAR Study Group. In this paper, we present an audit aiming to assess which of these criteria performs better in clinical practice.
Methods: Sixty-nine (69) patients with evidence of PsA were seen in the clinic as regular outpatients and were assessed as to whether they fulfil any of the 6 existing criteria for PsA: M & W, Bennett's, V & E, Fournié's, ESSG and CASPAR criteria. All items included in the 6 sets of criteria were recorded for each patient based on interview, clinical examination and scrutiny of clinical medical records. By comparing the criteria between themselves as well as the items used in each one of them we tried to assess which one of the criteria was performing best.
Results: A total of 69 patients (M/F=24/45; mean age 46.4 years (+/-20.3), and delay in diagnosis of 3.4 years (+/-4.1) was assessed. From those, 9 patients did not fulfil any criteria and excluded from the analysis. From the remaining 60 patients [M/F=21/39; (age 48+/-15.3)], 21 patients (35%) fulfilled all 6 sets of criteria. The remaining 39 patients (M/F=41/59 %; age 47+/-14.9) were further analysed with regards to the feature that did not enable concordance. From those 39 patients, Bennett's criteria were positive in only 4/39 (10.2%), M & W criteria were positive in 12/39 (30.7%), ESSG criteria in 17/39 (43.5%), V & E criteria were positive in 18/39 (46.1%), Fournié's criteria were positive in 31/39 (79.4%) and CASPAR criteria in 35/39 (89.7%). By including family history of psoriasis in the criteria, 11/39 patients (28.2%), who did not fulfil M & W or V & E due to lack of family history of psoriasis as item, met the CASPAR criteria. In addition, some patients who did not fulfil the M & W criteria, since RF positive (7/39; 17.9%), were able to satisfy the CASPAR criteria.
Conclusions: Family history of psoriasis is the main advantage of the new CASPAR Criteria over M & W and V & E. In addition, using the CASPAR criteria, it is possible to make a diagnosis of PsA in a patient who develops inflammatory articular disease even if with RF positive and polyarticular symmetrical arthritis. It is also important to have these classification criteria for the development of recommendations for the optimal treatment of patients with PsA. We believe that the CASPAR criteria, which are simple and easy to use, have high potential to be introduced as the universal classification criteria for PsA. However, further study of the validation of these new criteria is required.