Evaluation of pre-processing methods for tear fluid proteomics using the Olink platform

Abstract

Tear fluid forms a potential source for biomarker identification, and can be minimal invasively collected via Schirmer strips. The lack of knowledge on the processing of Schirmer strips however complicates the analysis and between-study comparisons. We studied two different pre-processing methods, specifically the use of punches of the strip versus elution of the strip in PBS buffer. Tear fluid filled Schirmer strips were collected from 5 healthy participants, and divided into two halves over the length of the strip. In either part, punches or eluates were obtained from 4 different locations, from the first part touching the eye (head) to the end, to assess the protein distribution along the strips. The levels of 92 inflammatory proteins were measured in the punches/eluates using Olink Target 96. The punch method yielded higher protein detectability compared to the elution method (76% vs 66%; p ≤ 0.001). However, 3 out of 5 punches from the head failed quality control. Protein levels over the remaining parts of the strips were similar. Based on our findings we encourage using the punch method of any part of the strip except the head with Olink Target 96 or other suitable techniques.