Global practices of tear fluid collection, storage, and molecular analysis - A questionnaire by the Tear Research Network

PURPOSE: While tear fluid biomarkers are now widely studied, agreement on best practices for sample collection, storage, processing and analysis is still being built. To promote the application of tear fluid biomarkers and to encourage the generation of high-quality data, the aim of this survey was to understand current practices and perspectives. METHODS: The Tear Research Network coordinated a self-administrated, digital survey between April 2023 and April 2024. The survey obtained information from 59 independent investigators and laboratories across 21 countries on demographics, tear fluid collection methods, storage conditions, processing steps, analysis techniques, and current and future perspectives for tear fluid research. RESULTS: Most respondents were based in the US (24%), followed by the UK and India (10% each). Schirmer's strips were the preferred tear collection method (44%). Protein assays were the most favoured analytical technique overall (47%) and for tear fluid collected with Schirmer's strips (42%). More than 80% of the laboratories did not employ normalization strategies to account for sample volume variability in collection methods other than Schirmer's strips and capillaries. A significant majority (91%) agreed on the need to develop internationally accepted guidelines, with 81% indicating that they would modify their protocols accordingly. CONCLUSIONS: This survey provides a global overview of tear fluid biomarker research practices, highlighting substantial variability in methodologies and a pressing need for standardised protocols. Addressing these inconsistencies through international guidelines could enhance reproducibility, facilitate global collaboration, and accelerate the clinical translation of tear fluid biomarkers.