Incidence of physician-diagnosed primary Sjogren syndrome in residents of Olmsted County, Minnesota

Objectives: To estimate the incidence of physician-diagnosed primary Sjogre n syndrome (SS) among residents of Olmsted County, Minnesota, in the settin g of usual medical care and to determine how often objective criteria are a vailable in the medical records of such patients. Patients and Methods: We reviewed all medical records of residents in Olmst ed County with physician-diagnosed SS from 1976 to 1992 to determine whethe r they had undergone objective tests for keratoconjunctivitis sicca, saliva ry dysfunction, or serologic abnormality. Confounding illnesses were exclud ed. To identify misclassified eases, all records from patients with xerosto mia or keratoconjunctivitis sicca were also reviewed. The average annual SS incidence rates were calculated by considering the entire population to be at risk. Results: Of 75 patients with onset of SS during the study period, 53 had pr imary SS, All patients were white, 51 (96.2%) were women, and the mean +/- SD age was 59 +/- 15.8 years. The age- and sex-adjusted annual incidence wa s 3.9 per 100,000 population (95% confidence interval, 2.8-4.9) for patient s with primary SS, Eleven patients (20.8%) with physician-diagnosed SS had no documentation of objective eye, mouth, or laboratory abnormalities. Obje ctive evaluations performed most frequently were laboratory and ocular test s and least often were investigations of xerostomia, Conclusions: The average annual incidence rate for physician-diagnosed prim ary SS in Olmsted County is about 4 cases per 100,000 population, These dat a probably underestimate the true incidence because they are based on usual medical care of patients with SS in a community setting, rather than on a case-detection survey, In the future, a true incidence may be possible with a higher index of suspicion, greater attention to objective tests, and inc reased awareness of new classification criteria for SS, For epidemiological studies based on existing data, application of current criteria may not be feasible, and consensus on criteria for such studies would be useful.