Prevalence of Primary Sjögren's Syndrome in a US Population-Based Cohort.

OBJECTIVE: To report the point prevalence of primary Sjögren's syndrome (SS) in the first US population-based study.

METHODS: Cases of all potential primary SS patients living in Olmsted County, Minnesota, on January 1, 2015, were retrieved using Rochester Epidemiology Project resources, and ascertained by manual medical records review. Primary SS cases were defined according to physician diagnosis. The use of diagnostic tests was assessed and the performance of classification criteria was evaluated. The number of prevalent cases in 2015 was also projected based on 1976-2005 incidence data from the same source population.

RESULTS: A total of 106 patients with primary SS were included in the study: 86% were female, with a mean ± SD age of 64.6 ± 15.2 years, and a mean ± SD disease duration of 10.5 ± 8.4 years. A majority were anti-SSA positive (75%) and/or anti-SSB positive (58%), but only 22% met American-European Consensus Group or American College of Rheumatology criteria, because the other tests required for disease classification (ocular dryness objective assessment, salivary gland functional or morphologic tests, or salivary gland biopsy) were rarely performed in clinical practice. According to the physician diagnosis, the age- and sex-adjusted prevalence of primary SS was 10.3 per 10,000 inhabitants, but according to classification criteria, this prevalence was only 2.2 per 10,000. The analysis based on previous incidence data projected a similar 2015 prevalence rate of 11.0 per 10,000.

CONCLUSION: The prevalence of primary SS in this geographically well-defined population was estimated to be between 2 and 10 per 10,000 inhabitants. Physicians rarely used tests included in the classification criteria to diagnose the disease in this community setting.