[Tear lactoferrin in keratoconjunctivitis sicca].

Keratoconjunctivitis sicca is a commonly encountered disease with decreased lacrimal gland activity. There are several tests to determine the lacrimal gland function, but all have limitations in accuracy, sensitivity or technical difficulty. At present, there is no reliable objective test to render a firm diagnosis of dry eye. Lactoferrin is one of the major proteins secreted by the lacrimal gland. Its concentration was found to correlate well to lacrimal gland activity. In this study we tried to evaluate the diagnostic value of lactoferrin measurement in comparison with other tests for keratoconjunctivitis sicca. Tests including the measurement of tear lactoferrin, Schirmer's-1 test, Schirmer's basal test, tear film break-up time, and rose bengal stain of the cornea were done on 60 healthy eyes and 56 eyes with keratoconjunctivitis sicca. The lactoferrin level was measured by a commercially available "Lactoplate" (Eagle Vision, U.S.A.). It is a plate containing gel loaded with rabbit anti-human-lactoferrin antiserum. Tear-moistened filter paper discs containing lactoferrin were placed on the gel. The lactoferrin concentration could be determined by measuring the concentric ring of precipitate after 72 hours incubation at room temperature. The average concentration of lactoferrin was 1.9 +/- 0.51 mg/ml in the normal group and 1.4 +/- 0.93 mg/ml in the keratoconjunctivitis sicca group. They were significantly different from each other (t-test: p less than 0.05). The results of the other 4 tests also showed a significant difference between the normal and keratoconjunctivitis sicca group, but the lactoferrin measurement had the highest specificity among these 5 tests. Because of the technical simplicity of measurement and its high specificity, lactoferrin measurement could be a valuable tool for the early and accurate diagnosis of keratoconjunctivitis sicca.