Tear lysozyme activity in frozen Schirmer strips and salivary gland biopsyas parameters of lacrimal gland function

Purpose: The lysozyme concentration in human tears is an important paramete r for tear gland function. The decline of lysozyme in tears reflects lacrim al gland destruction. In Sjogren's patients,:lacrimal gland destruction par allels labial salivary gland destruction. The objective of this study was t o determine whether human tear lysozyme that was frozen on Schirmer strips at -20 degrees C for several years maintained activity and whether there wa s a linear relation with inflammatory changes in labial salivary glands. Me thods: A total of 200 frozen Schirmer strips were processed. They were coll ected from to randomly selected patients each year of five consecutive year s, all attending the UCSF Sjogren's Clinic. The tear lysozyme in the Schirm er strips was measured by a calorimetric assay. The average lysozyme concen tration each year was calculated and compared. One third of the patients un derwent labial salivary gland biopsy. The correlation was calculated betwee n the tear lysozyme concentration and the lymphocytic focus scores in biops y specimens. Results: No significant difference of average lysozyme concent ration in the Schirmer strips was found when the five different years of co llection were compared. The linear relation between the tear lysozyme conce ntrations and the focus score in labial salivary gland biopsies showed a co efficient of r = -0.41. The linear relation between other diagnostic measur ements, like Schirmer test, tear breakup time, or rose bengal staining patt ern, and the focus score was lower. Conclusions: Human tear lysozyme in Sch irmer strips can be stored at -20 degrees C far at: least five, years. Ther e is little difference in lysozyme activity of frozen compared to unfrozen specimens. The lysozyme concentration in tears correlates better with the l ymphocytic focus score in labial salivary gland biopsy than does clinical a ssessment and is therefore a parameter for the actual degree of tear gland destruction.