Prevalence of psoriatic arthritis in Italian psoriatic patients

To evaluate the prevalence of psoriatic arthritis (PsA) in Italian patients with psoriasis and to compare the Moll and Wright criteria, the European Spondylarthropathy Study Group (ESSG) criteria, and Amor criteria when applied to this patient population.

We examined 205 unselected patients with psoriasis. The diagnosis of PsA was based upon the clinical experience of a rheumatologist. After, we tested these classification criteria. HLA class I and II antigens were also analyzed.

Thirty-six percent (75) of psoriatic patients were considered by a clinical expert to have PsA. Moll and Wright criteria identified 46 patients (22%) with PsA; 49 patients (24%) were identified by ESSG criteria and Amor criteria; 12 patients identified by Amor criteria but not by ESSG criteria presented enthesitis or dactylitis; 10 patients identified by ESSG but not by Amor criteria had peripheral synovitis. In patients with peripheral arthritis and psoriasis, the evaluation of NSAID response was critical to fulfilling Amor criteria. However, it was not easy to retrospectively evaluate NSAID response using these criteria. The sensitivity was low for each of the 3 classification criteria (from 61 to 65%), whereas the specificity was high (from 99 to 100%).

Our study confirms a high prevalence of PsA among an unselected population of Italian patients with psoriasis. Our data reveal the inadequacy of the existing criteria for PsA, including the ESSG criteria and Amor criteria for the classification of spondyloarthropathy.