[Keratoconjunctivitis sicca in Sjögren's syndrome: diagnostic significance of relative protein composition of tears].

Six protein components were detected in the tears by exclusive high-pressure liquid chromatography. By their molecular weight, these components were identified as lacrimal prealbumin, human serum albumin, lactoferin, IgG, and IgA. The relative content of these proteins in tears correlates with the clinical picture of kerato-conjunctivitis sicca. Correlation coefficients (ci) were -0.66 for lysozyme, -0.58 for prealbumin, 0.70 for serum albumin, -0.63 for lactoferrin, and 0.65 for IgA. Linear regression analysis showed that the relative content of IgA and serum albumin rapidly increased in the course of disease. The relative content of lysozyme, lactoferrin, and prealbumin dropped, but two times slower. The authors propose assessing the quantitative changes in the lacrimal protein composition by a special diagnostic parameter: P = sigma(dni-di)ci/C, where dni and di are the mean relative levels of the protein component in health and disease, C the sum of absolute values of correlation coefficients for all components (C = sigma[ci]). The (dni-di) value reflects the effect of disease on changes in the relative content of each protein component and the ci/C value the intensity of this effect. This parameter can be used for assessing the involvement of the eyes in Sjogren's syndrome and monitoring the efficacy of treatment.