Tear lysozyme activity in frozen Schirmer strips and salivary gland biopsy as parameters of lacrimal gland function.

<bold>Purpose: </bold>The lysozyme concentration in human tears is an important parameter for tear gland function. The decline of lysozyme in tears reflects lacrimal gland destruction. In Sjögren's patients, lacrimal gland destruction parallels labial salivary gland destruction. The objective of this study was to determine whether human tear lysozyme that was frozen on Schirmer strips at -20 degrees C for several years maintained activity and whether there was a linear relation with inflammatory changes in labial salivary glands.<bold>Methods: </bold>A total of 200 frozen Schirmer strips were processed. They were collected from 20 randomly selected patients each year of five consecutive years, all attending the UCSF Sjögren's Clinic. The tear lysozyme in the Schirmer strips was measured by a colorimetric assay. The average lysozyme concentration each year was calculated and compared. One third of the patients underwent labial salivary gland biopsy. The correlation was calculated between the tear lysozyme concentration and the lymphocytic focus scores in biopsy specimens.<bold>Results: </bold>No significant difference of average lysozyme concentration in the Schirmer strips was found when the five different years of collection were compared. The linear relation between the tear lysozyme concentrations and the focus score in labial salivary gland biopsies showed a coefficient of r = -0.41. The linear relation between other diagnostic measurements, like Schirmer test, tear breakup time, or rose bengal staining pattern, and the focus score was lower.<bold>Conclusions: </bold>Human tear lysozyme in Schirmer strips can be stored at -20 degrees C for at least five years. There is little difference in lysozyme activity of frozen compared to unfrozen specimens. The lysozyme concentration in tears correlates better with the lymphocytic focus score in labial salivary gland biopsy than does clinical assessment and is therefore a parameter for the actual degree of tear gland destruction. [ABSTRACT FROM AUTHOR]