Epidemiology of psoriatic arthritis in the population of the United States.

BACKGROUND: Estimates of the prevalence of psoriatic arthritis vary widely and are usually not determined by population-based studies.

OBJECTIVES: We sought to determine the prevalence of psoriatic arthritis and the impact of the disease on quality of life in the US population.

METHODS: Patients were selected randomly from the US population and were interviewed by telephone. Cases were defined as patients who reported a physician diagnosis of psoriasis and psoriatic arthritis.

RESULTS: Interviews of 27,220 persons were conducted; 601 of the interviewees had psoriasis and 71 had psoriasis and psoriatic arthritis. The prevalence of psoriatic arthritis was 0.25% (95% confidence interval [CI]: 0.18%, 0.31%). The prevalence of psoriatic arthritis among patients with psoriasis was 11% (95% CI: 9%, 14%) and varied substantially based on self-reporting of the extent of skin involvement with psoriasis. Thirty-nine percent of patients with psoriatic arthritis indicated that it was a large problem in everyday life.

LIMITATIONS: Psoriatic arthritis was classified on the basis of the patient's self-report.

CONCLUSION: Psoriatic arthritis affects an estimated 520,000 patients in the US population, and many rate it as a large problem in everyday life. The prevalence varies widely based on the extent of skin involvement, which demonstrates the importance of performing broadly representative studies to measure the prevalence of psoriatic arthritis.