Prevalence, disease manifestations, and treatment of psoriatic arthritis in western Norway

Objective. To estimate the prevalence of psoriatic arthritis (PsA) in a geographically defined population, and to characterize the clinical manifestations and medical treatment for PsA. Methods. Prevalent cases were identified for the years 1999-2002 at the rheumatology centers for the population of 442,000 inhabitants. Clinical data were extracted from patient records. Cases with psoriasis and peripheral arthritis and/or radiographic evidence of spondyloarthritis were considered to have PsA, those with other arthritides were excluded. Results. In total, 634 patients with PsA were identified from the adult population, equivalent to a prevalence of 1.95 per 1000 (1.80-2.10). There were no significant sex differences in rates; for both sexes the prevalence was highest in the age group 40 to 59 years. Polyarthritis was the most frequent subclass (68.6%). Oligoarthritis, monoarthritis, and arthritis confined to the spine or sacroiliac joints were seen in 22.9%, 5.8%, and 2.7% of cases, respectively. Mean age was higher (50.6 yrs for all cases), and mean disease duration was longer (10.7 yrs) with increasing number of joints affected. The mean erythrocyte sedimentation rate and C-reactive protein were higher with increasing number of joints affected and disease duration. Intraarticular injection of glucocorticoids had been administered to 40.0% of the patients during the last year. Disease modifying antirheumatic drugs were used by 40.0%, with oral methotrexate being the most frequently used. Conclusion. The estimated prevalence of PsA was 1.95 per 1000 adult inhabitants, which is higher than previously reported. The demographic data support the presence of a shift from mono- and oligoarthritis to polyarthritis and increased inflammatory activity with increasing disease duration. Methotrexate and intraarticular glucocorticoids were frequently used treatments.