Diagnostic usefulness and cutoff value of Schirmer's I test in the Japanese diagnostic criteria of dry eye

Background: Recently, the diagnostic criteria of dry eye have been tentatively approved in Japan. The aim of this study was to evaluate the diagnostic usefulness and the cutoff value of Schirmer's I test on applying these Japanese diagnostic criteria to patients with Sjogren's syndrome. Methods: One hundred eyes of 50 patients with Sjogren's syndrome underwent a series of diagnostic tests, including Schirmer's I test, cotton thread test, tear film break-up time (BUT), fluorescein staining, and rose bengal staining. They were classified into definite dry eye, probable dry eye, and normal eye according to the Japanese criteria. The diagnostic usefulness of Schirmer's I test was evaluated in comparison with that of the cotton thread test or BUT, based on the diagnostic outcome by combination of the individual tests plus vital staining tests. The cutoff value of Schirmer's I test was evaluated, based on the results of sensitivity and specificity rates at each cutoff value from 0 to 10 mm. Results: The diagnostic usefulness of Schirmer's I test was inferior to that of BUT, but superior to that of cotton thread test. The sensitivity and specificity were 80% and 53%, respectively, at a cutoff value of 5 mm and 88% and 35%, respectively, at a cutoff value of 10 mm. Conclusion: In investigation of dry eye, both Schirmer's I test and BUT should be performed to detect tear abnormalities. The cutoff value of 5 mm in Schirmer's I test seems to be justified provided that the purpose of the test is comparison of inter-institutional data, not screening.