title: Intra- and inter-day variation of cytokines and chemokines in tears of healthy subjects.
abstract: Tear levels of certain cytokines/chemokines can potentially serve as biomarkers for dry eye and other ocular surface diseases if they remain stable from day-to-day in healthy eyes. The aim of this study was to determine the normal intra- and inter-day variation of selected tear cytokines/chemokines. Tear samples from 24 young, healthy adults were collected 11:00 AM-1:00 PM (mid-day) and 5:00-7:00 PM (evening) on three non-consecutive days. Concentrations of 18 cytokines/chemokines (EGF, eotaxin, CX3CL1/fractalkine, GM-CSF, IFN-γ, IL-10, IL-1β, IL-13, IL-17A, IL-1RA, IL-5, IL-6, CXCL8/IL-8, IL-9, CXCL10/IP-10, CCL5/RANTES, TNF-α, and VEGF) were measured by multiplex bead analysis. Ocular surface disease was ruled out by clinical tests. A random-effects ANOVA model was used to evaluate intra- and inter-day effects on cytokine/chemokine levels. Repeatability of intra-subject inter-day measurements was assayed by coefficient of variation. Ten out of the 18 molecules had detectable tear levels in >50% of the subjects. Of those, only IL-10 and IL-1β levels had significant inter-day variations. EGF, CX3CL1/fractalkine, CXCL10/IP-10, and VEGF were consistently higher in the evening compared to the mid-day measurements. EGF, CXCL10/IP-10, VEGF and CXCL8/IL-8had good intra-subject reproducibility. In conclusion, tear cytokines/chemokines can be measured reproducibly over time, with most not having significant inter-day variability. Some varied significantly depending upon the time of tear collection, and these variations should be taken into account when comparisons are made. The good intra-subject reproducibility for EGF, CXCL10/IP-10, CXCL8/IL-8, and VEGF indicates that these molecules could potentially serve as biomarkers of ocular surface disease.
authors.affiliation: IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain.
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Benito
authors.affiliation: IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Valladolid, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: González-García
authors.affiliation: IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain.
authors.forename: Marisa
authors.initials: M
authors.lastname: Tesón
authors.affiliation: IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain.
authors.forename: Noelia
authors.initials: N
authors.lastname: García
authors.affiliation: Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Valladolid, Spain; IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain.
authors.forename: Itziar
authors.initials: I
authors.lastname: Fernández
authors.affiliation: IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Valladolid, Spain.
authors.forename: Margarita
authors.initials: M
authors.lastname: Calonge
authors.affiliation: IOBA - University of Valladolid, Campus Miguel Delibes, Paseo de Belén 17, Valladolid E-47011, Valladolid, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Valladolid, Spain. Electronic address: amalia@ioba.med.uva.es.
authors.forename: Amalia
authors.initials: A
authors.lastname: Enríquez-de-Salamanca
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000378:metabolism*; D018925:Chemokines / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D013666:Tears / Q000378:metabolism*; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D018925:Chemokines; D016207:Cytokines; D005136:Eye Proteins; C042434:tear proteins
keywords: chemokine; circadian rhythm; cytokine; tears