Abstract: Correlation of inflammatory cytokines with 4 diagnostic tests

Bottom line of this study was that both Schirmer (the little strip test we love to hate) and tear osmolarity correlated better with the presence of inflammatory cytokines and MMPs (i.e. evidence of inflammation) than the OSDI questionnaire or the classic TBUT test.

Correlation of tear inflammatory cytokines and matrix metalloproteinases with four dry eye diagnostic tests.

Purpose.
Tear cytokines and matrix metalloproteinases (MMPs) can be extracted from the Schirmer strip. This study examined the extracted levels of tear cytokines and MMPs from Schirmer strips and potential correlation with Schirmer's test, tear breakup time (TBUT), tear osmolarity, and ocular surface disease index (OSDI).

Methods.
Thirty healthy volunteers were clinically evaluated for known methods to diagnose dry eye disease, including Schirmer's test, tear osmolarity, OSDI, and TBUT. Tears were collected by Schirmer strips and proteins were extracted from the Schirmer strip in 0.5 M NaCl with 0.5% Tween 20 and analyzed using Luminex kits to examine cytokines or MMPs. Calculated cytokine and MMP concentrations for all samples were sorted into groups according to a positive or negative for each of the above 4 dry eye diagnostic tests individually and in combination.

Results.
Five inflammatory cytokines (IL-1α, IL-1β, IL-6, IL-8, and TNF-α) and 5 MMPs (MMPs 1, 2, 7, 9, and 10) were extracted from clinical Schirmer strips. Schirmer strip measurement and tear osmolarity correlated well with increased concentrations of the inflammatory cytokines and MMPs, while TBUT and OSDI did not.

Conclusions.
Both the Schirmer's test and tear osmolarity may be more relevant to the clinician in the diagnosis of ocular surface diseases with an increased level of inflammatory mediators.

Invest Ophthalmol Vis Sci. 2012 Feb 8. [Epub ahead of print]
Vandermeid KR, Su SP, Ward KW, Zhang JZ.