title: The fall and rise of tear albumin levels: a multifactorial phenomenon.
abstract: Albumin in tears is used as a diagnostic marker of ocular insult and inflammation, but whether its presence in tears is responsive or part of an adaptive reaction remains unresolved. A review of the literature on tear albumin concentration emphasizes that variables such as collection method, stimulus, assay technique, and disease state influence the quoted values to different extents. Influence of assay technique is negligible in comparison to variation in sampling conditions. Ocular disease increases albumin concentrations but not in a specific manner. The literature review also highlighted that little systematic research has been carried out on the daily cycle of tear albumin levels. In order to remedy this shortcoming, we investigated variations in tear albumin concentration during the waking day. The concentration of albumin in 400 tear samples collected from 13 subjects was assessed at 2-hourly intervals throughout the waking day. Highest daytime albumin concentrations were obtained within 10 minutes of waking, with a mean concentration of >50 ± 22 μg/ml. Albumin levels were at their lowest, but most consistent, 2-6 hours post-waking. This pattern was followed by a progressive increase in albumin concentration during the latter part of the day. Although individual subject-to-subject concentration differences were observed, this distinctive pattern of diurnal variation was found in all subjects. The results presented suggest a regulated, not random, pattern of variation within the period of study.
authors.affiliation: Biomaterials Research Unit, School of Engineering and Applied Chemistry, Aston University, Birmingham, B4 7ET, UK.
authors.forename: Gunilla
authors.initials: G
authors.lastname: Runström
authors.forename: Aisling
authors.initials: A
authors.lastname: Mann
authors.forename: Brian
authors.initials: B
authors.lastname: Tighe
mesh_terms: D000418:Albumins / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D005136:Eye Proteins / Q000737:chemistry*; D006801:Humans; D012621:Seasons; D013666:Tears / Q000737:chemistry*
chemical_list: D000418:Albumins; D005136:Eye Proteins
keywords: albumin; biomarker; diurnal shift; mucosal fluids; tear composition; tear sampling; vascular permeability