title: Substance P in Flush Tears and Schirmer Strips of Healthy Participants.
abstract: To determine the repeatability of the flush tear collection technique and the Schirmer strip for Substance P tear analysis.
  
  
  
  The tears of 10 healthy non-contact-lens wearers were collected via Schirmer strip and microcapillary following instillation of either 20 μL (F-20) or 60 μL (F-60) of saline. Each technique was conducted on two occasions and in a randomized order. Total protein content (TPC) and Substance P concentrations were determined. The overall protein separation profile of each type of tears was examined using one-dimensional gel electrophoresis (1DGE).
  
  
  
  Collection rates were significantly faster for the F-60 compared to F-20 (17.3 ± 6.9 μL/min and 11.9 ± 5.3 μL/min, respectively, P < .001), with an average Schirmer strip length of 1.5 ± 2.1 mm/min. The coefficient of repeatability between days and eyes was greatest for the Schirmer strip, with eyes and days being significantly different (P = .03 and P = .03, respectively) for Schirmer strip Substance P. TPC was 3.8 ± 2.6 mg/mL, 3.3 ± 1.8 mg/mL, and 3.6 ± 3.0 mg/mL for F-20, F-60, and Schirmer strip techniques, respectively, with no significant difference between techniques (P = .85). Substance P concentration was 13.1 ± 14.8 ng/mL, 9.1 ± 6.1 ng/mL, and 14.9 ± 10.6 ng/mL for F-20, F-60, and Schirmer strip tears, respectively, with no significant difference between techniques (P = .57). 1DGE profile showed similar electrophoresis patterns among F-20, F-60, and basal tears.
  
  
  
  The F-60 method allows faster collection than F-20, but the latter results in better repeatability than both the F-60 and Schirmer sampling techniques. All three techniques return the same concentrations of TPC and Substance P. This indicates that tear collection using the F-20 may be more appropriate when conducting comparative analysis, whereas the F-60 may be more appropriate when more volume is required.
authors.affiliation: *PhD, MOptom, FAAO †PhD School of Optometry and Vision Science, University of New South Wales, Sydney, Australia (MM, JY); Deakin Optometry, Deakin University, Waurn Ponds, Victoria, Australia (MG); and University of Sydney, SaveSight Institute, Sydney, New South Wales, Australia (MM, JY).
authors.forename: Maria
authors.initials: M
authors.lastname: Markoulli
authors.forename: Moneisha
authors.initials: M
authors.lastname: Gokhale
authors.forename: Jingjing
authors.initials: J
authors.lastname: You
mesh_terms: D000328:Adult; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000032:analysis*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000295:instrumentation / Q000379:methods; D013373:Substance P / Q000032:analysis*; D013666:Tears / Q000737:chemistry*
chemical_list: D005136:Eye Proteins; C042434:tear proteins; D013373:Substance P