The lactoferrin test for the diagnosis of keratoconjunctivitis sicca in clinical practice.

Tear fluid lysozyme concentration, measured by means of the agar diffusion assay, and lactoferrin concentration, measured with radial immunodiffusion using the Lactoplate test, were determined in 112 persons in routine clinical practice. About one third of these persons had symptoms and signs compatible with keratoconjunctivitis sicca. A good correlation was found between these tear proteins in the tear fluid in persons with normal tear function and in those with a tear function disorder. In 8%, false-positive and false-negative results were obtained, but the difference in associated values of lysozyme and lactoferrin concentration was small.