title: The effect of storage conditions on salivary cortisol concentrations using an enzyme immunoassay.
abstract: Saliva samples are easy to collect and are applicable for home-sampling, e.g. when studying HPA-axis dynamics to characterize diurnal cortisol profiles and the cortisol awakening response. However, the storing and transport conditions might be critical in the home-sampling approach. Here, we tested the stability of saliva cortisol in samples stored at different temperatures and after repeated thawing-freezing cycles when measured with an Enzyme Immuno Assay (EIA). Thirteen healthy volunteers, six women and seven men, mean age 31 (range 26-49) years collected saliva either in the morning hours (08:00-10:00 h) or before lunch (11:00-12:00 h). Storage at six different conditions were tested: Storage at - 18°C, - 4°C, 4°C and room temperature for 72 h. One condition tested was at - 18°C for 72 h and then kept in an envelope for 72 h with a freezing element in room temperature surroundings where after it was stored at - 80°C. The last tube was stored directly at - 80°C and served as the 'gold standard'. The saliva samples were assayed using Salivary Cortisol Diagnostic EIA. Differences in cortisol measurements between each of the five conditions and the 'gold standard' (- 80°C) were evaluated by one-sample t-test. No significant differences were observed. This indicates that an EIA method can be used reliably when measuring salivary cortisol samples obtained by home-sampling including a postal delivery.
authors.affiliation: Neurobiology Research Unit and Center for Integrated Molecular Brain Imaging (CIMBI), Copenhagen University Hospital , Rigshospitalet, Section 9201, Copenhagen , Denmark.
authors.forename: Anjana A
authors.initials: AA
authors.lastname: Nalla
authors.forename: Gerda
authors.initials: G
authors.lastname: Thomsen
authors.forename: Gitte M
authors.initials: GM
authors.lastname: Knudsen
authors.forename: Vibe G
authors.initials: VG
authors.lastname: Frokjaer
mesh_terms: D000328:Adult; D015925:Cryopreservation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012463:Saliva
chemical_list: D006854:Hydrocortisone
keywords: Cortisol; Enzyme Immuno Assay; HPA-axis; saliva; stability; storage