The effect of storage conditions on salivary cortisol concentrations using an Enzyme Immunoassay.

The effect of storage conditions on salivary cortisol concentrations using an Enzyme Immunoassay.
Scand J Clin Lab Invest. 2014 Dec 16;:1-4
Authors: Nalla AA, Thomsen G, Knudsen GM, Frokjaer VG
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.
PMID: 25510953 [PubMed – as supplied by publisher]
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