Background Different studies worldwide reported highly discrepant estimates for the prevalence of primary Sjögren's syndrome (pSS), ranging from 0.01% of the general population to more than 3%. No previous study reported the prevalence of pSS in the United States.
Objectives To report the 2015 point prevalence of pSS in the first population-based study performed in the U.S.
Methods Cases of all potential pSS patients living in Olmsted County, Minnesota on January 1, 2015 were retrieved using the Rochester Epidemiology Project resources, and ascertained by manual medical record review. Definite pSS cases were defined according to physician diagnosis. All patients with doubtful cases and all patients with an associated systemic autoimmune disease were excluded. The use of diagnostic tests was assessed and the performance of classification criteria in this community-based cohort 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 pSS were included in the study: 86% were female, with a mean (SD) age of 64.6 (15.2) years and 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 were rarely performed in clinical practice (ocular dryness objective assessment, salivary gland functional or morphologic tests, or salivary gland biopsy). According to the physician diagnosis, age and sex adjusted prevalence of pSS was 10.3/10,000 inhabitants, but according to classification criteria this prevalence would be only 2.2/10,000. The analysis based on previous incidence data projected a similar 2015 prevalence rate of 11.0/10,000. Using figures from the 2015 general U.S. population census, a total of 248,000 patients with pSS (35,000 males and 213,000 females) would currently live in the country. If only cases fulfilling classification criteria are considered, there would be only about 53,000 prevalent cases of pSS in the U.S.
Conclusions This study reports the first prevalence rate of physician-diagnosed pSS in a well-defined population in the U.S. The estimated prevalence of 10.3/10,000 inhabitants in 2015 is higher than previous results obtained in other geographical areas, probably due to different methodological designs of the studies. Because physicians rarely used tests included in the classification criteria to diagnose the disease in this community setting, current classification criteria do not reflect accurately the diagnosis of pSS in routine clinical practice.
Disclosure of Interest None declared