Abstract
Tear fluid is receiving growing attention as a source for novel diagnostic biomarkers. Multiple techniques are available for its collection and impact the composition of acquired samples. We sought to provide a direct comparison of two collection methods with regard to implementation, acceptance, and impact on sample composition. Tear fluid was collected from fifteen healthy volunteers with capillary tubes and Schirmer strips and analyzed for total protein and IgG concentrations. Sampling parameters and perception by test persons were compared. The use of capillary tubes was more convenient for the participants while causing more effort for the collector. Tear flow rates as well as the relative and absolute amount of IgG were higher when Schirmer strips were used. Consecutive collections with Schirmer strips significantly influenced tear flow rates, IgG, and protein concentrations. A moderate correlation was observed between tear flow rates and IgG concentrations for both methods. Samples collected with both methods can be analyzed by isoelectric focusing, a potential diagnostic application in the field of neurology. The specific advantages and limitations of tear fluid sampling with either capillary tubes or Schirmer strips demonstrate the need for a thorough investigation of collection methods with regard to the application of interest.
Highlights
Tear fluid is receiving growing attention as a source for novel diagnostic biomarkers
We were interested in total protein and immunoglobulin G (IgG) concentrations
The main focus was the collection of tear fluid without stimulation at a volume allowing for further laboratory analysis in a way that can be implemented in clinical routine and is convenient to the patient
Summary
Tear fluid is receiving growing attention as a source for novel diagnostic biomarkers. Tear fluid was collected from fifteen healthy volunteers with capillary tubes and Schirmer strips and analyzed for total protein and IgG concentrations. Consecutive collections with Schirmer strips significantly influenced tear flow rates, IgG, and protein concentrations. A moderate correlation was observed between tear flow rates and IgG concentrations for both methods Samples collected with both methods can be analyzed by isoelectric focusing, a potential diagnostic application in the field of neurology. The most commonly described techniques for the collection of tear fluid are Schirmer strips and capillary tubes[16] For these methods, numerous protocols have been applied, potentially influencing the composition and quality of obtained samples and introducing a considerable variability among studies[17,18,19]. The tear film is part of the mucosal immune system, contains immunoglobulins, and provides further possibilities for research questions involving humoral immunity[28,29,30]
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