Diagnostic biomarkers in tear fluid: from sampling to preanalytical processing

Area of Science:

• Biomarker Discovery
• Ophthalmology
• Clinical Chemistry

Background:

• Tear fluid is increasingly recognized as a valuable source for novel diagnostic biomarkers.
• Various tear collection techniques exist, each potentially influencing sample composition and diagnostic accuracy.

Purpose of the Study:

• To directly compare capillary tubes and Schirmer strips for tear fluid collection.
• To evaluate implementation, participant acceptance, and impact on sample composition (total protein, IgG).

Main Methods:

• Tear fluid collection from 15 healthy volunteers using both capillary tubes and Schirmer strips.
• Analysis of total protein and immunoglobulin G (IgG) concentrations.
• Comparison of sampling parameters and participant perceptions.

Main Results:

• Schirmer strips resulted in higher tear flow rates and concentrations of IgG and total protein compared to capillary tubes.
• Consecutive Schirmer strip collections significantly altered tear flow, IgG, and protein levels.
• Capillary tubes offered greater participant convenience but required more effort from the collector.

Conclusions:

• The choice of tear collection method (capillary tubes vs. Schirmer strips) significantly impacts sample composition and tear flow dynamics.
• Understanding these differences is crucial for selecting the appropriate method based on the specific diagnostic application.
• Both methods yield samples suitable for techniques like isoelectric focusing, relevant for neurological diagnostics.