Purpose: To determine the clinical value of serological testing in patients with idiopathic scleritis. Design: Retrospective case series. Methods: Medical records of patients with scleritis seen at an institutional referral center over an 11-year period were reviewed. Results: Of 119 patients with scleritis seen at the University of Illinois Uveitis Clinic, 91 (76.5%) patients had no known etiology at initial presentation. Seventy of the 91 patients were tested for rheumatoid factor (RF), 19 (27.1%) of whom had a positive result. Ten (52.6%) of these RF positive patients were subsequently diagnosed with rheumatoid arthritis (RA) during a mean follow-up of 10.6 months (range, zero to 72 months), whereas only one of 51 (2.0%) RF negative patients developed RA, producing an odds ratio for developing RA in RF positive patients of 55.6 (95% confidence interval (CI) 7.8 to 369.8, P = .00001). Of the 70 patients who were tested for anti-neutrophil cytoplasmic antibody (ANCA), seven (10.0%) tested positive. Three (42.9%) of the ANCA positive patients subsequently developed Wegener granulomatosis (WG), whereas only two of 63 ANCA negative patients (3.2%) developed WG during a mean follow-up of 8.4 months (range, zero to 72 months). The odds ratio for developing WG in patients with idiopathic scleritis and a positive ANCA screen compared with a negative ANCA was 22.9 (95% CI 3.4 to 154.2, P = .006). Conclusions: The likelihood of patients with idiopathic scleritis developing RA and WG was increased if they had a positive RF or ANCA, supporting the role of immunologic marker testing in patients who present without systemic disease.
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