Figure S3. Stability of CatS activity in tear fluid upon storage at − 80 °C. Specifically, tear fluid was stored at − 80 °C on the day of sample acquisition for 7–8 days until the first measurement. After testing, they were re-stored at − 80 °C over a period of 6 (HC1 and pSS2) and 8 (pSS1) weeks, respectively, until the second measurement. As indicated, CatS activity was stable, with a trend towards higher levels in the second test, but below 20% of variation, which is considered acceptable for bioassays. (PPTX 67 kb)