Background: Psoriasis is a predictor of morbidity. It is important to determine the extent to which psoriasis remains undiagnosed.
Objective: To determine the prevalence of psoriasis.
Methods: We conducted a cross-sectional study using the National Health and Nutrition Examination Survey 2003-2004.
Results: The prevalence of diagnosed psoriasis was 3.15% (95% confidence interval [CI], 2.18-4.53), corresponding to 5 million adults. Approximately 17% of these patients have moderate to severe psoriasis based on body surface area report and 25% rate psoriasis a large problem in everyday life. The prevalence of undiagnosed active psoriasis by conservative estimate was 0.4% (95% CI, 0.19-0.82), corresponding to approximately 600,000 US adults, and 2.28% (95% CI, 1.47-3.50) by a broader definition, corresponding to 3.6 million US adults. Undiagnosed patients had a trend toward being more likely to be male, nonwhite, less educated, and unmarried compared with patients who had received a diagnosis.
Limitations: The method for determining the presence of psoriasis had limited ability to detect mild disease and only fair interrater agreement.
Conclusion: More than 5 million adults have been diagnosed with psoriasis. A large number have undiagnosed psoriasis and there are important disparities which may be associated with not receiving medical attention.