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A. Enriquez-De-Salamanca, M. Tesón, N. García, L. Mena, A. Sacristán, M. J. Benito, I. Fernández, M. Calonge, M. E. Stern, M. J. González; Cytokine and Chemokine Tear Levels in Healthy Subjects; Intra- and Inter-Day Variation Study. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4147.
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Tear levels of some cytokines/chemokines have been described as potential biomarkers for dry eye diagnosis. The aim of this study was to determine if the tear levels of a wide panel of cytokines/chemokines from healthy subjects vary depending on the time of the day and/or in samples taken in different days.
4 microliters of tears were collected non-traumatically with a capillary tube from one eye (randomly selected) of 24 healthy subjects (7 men, 17 women; mean age 21.41±3.25, range 18-30 years). Samples were obtained from the lateral canthus so as to avoid the tear reflex as much as possible, and were placed into collection tubes containing 16 microliters of buffer. The concentration of 18 cytokines/chemokines: EGF, Eotaxin, Fractalkine, GM-CSF, IFN-γ, IL-10, IL-1β IL-13, IL-17, IL-1RA, IL-5, IL-6, IL-8, IL-9, IP-10, RANTES, TNF-α, and VEGF was measured by a multiplex bead analysis. Ocular surface disease was ruled out by the following tests: OSDI questionnaire, slit-lamp examination, Schirmer test, Phenol read thread test, tear break-up time (T-BUT) and fluorescein corneal staining. Tear samples were collected at two different times of the day: between 11:00 and 13:00 h and between 17:00 and 19:00 h, and on three non-consecutive days, with a total of 6 visits. Random-Effects ANOVA model was used to evaluate intra- and inter-day effect on molecule levels.
Eotaxin, GM-CSF, IFN-γ, IL-17, IL-5, IL-9, and TNF-α tear levels were below the detection limit (3.2 pg/ml) in every sample; IL-1β, IL-6, IL-10, IL-13, and VEGF were detected in a variable percentage of samples. EGF, Fractalkine, IL-1RA, IL-8, IP-10, and RANTES were consistently detected in every sample. There were significant differences in EGF, Fractalkine, IP-10 and RANTES tear levels depending upon collection time (consistent for the three days), being higher in the 17:00 -19:00 h range than in the 11:00-13:00 h range. IL-1RA, and IL-8 tear levels showed no significant intra-day variation. There were no significant differences in cytokine tear levels among the days.
Collection time of tear samples affect some cytokine and chemokine levels. This indicate that samples to be compared must be collected at similar time intervals at least when EGF, Fractalkine, IP-10 and RANTES are determined.
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