The Comparison of Salivary Cortisol Immunoassay Kits: Correlations between Salivary and Plasma Cortisol Concentrations and Comparison of Immunoassay Methods / 日本補完代替医療学会誌

ABSTRACT

<i>Objective</i> The purpose of this study was to compare the performance of the salivary cortisol immunoassay kits that were manufactured by DRG International, Inc., Salimetrics, LLC., and IBL Hamburg, which were widely used in neuroendocrine research. Correlations between plasma and salivary cortisol concentrations and between enzyme-linked immunosorbent assay (ELISA) and luminescence immunoassay (LIA) were investigated.<br> <i>Methods</i> Saliva and plasma samples were collected in eight participants who took part in the study of the exercise stress testing. In total, forty salivary cortisol samples were assayed by means of the three salivary cortisol immunoassay kits. Plasma cortisol concentrations were determined by ELISA kit (IBL).<br> <i>Results</i> Salivary cortisol concentrations measured by the three immunoassay kits were significantly and highly correlated with plasma cortisol concentrations (r ≥ .863). Scattergrams also indicated that exponential curve well explained the relationship between salivary and plasma cortisol concentrations (r ≥ .925). Salivary cortisol concentrations measured by LIA (IBL) was correlated with salivary cortisol concentrations measured by ELISA (DRG and Salimetrics r=.943 and .985, respectively). Values of cortisol concentration measured by ELISA (DRG) were higher than those by ELISA (Salimetrics) and LIA (IBL).<br> <i>Conclusion</i> Salivary cortisol concentrations that were measured by the three immunoassay kits reflected the variations of plasma cortisol concentration. Differences in immunoassay methods (ELISA and LIA) did not influence the values of cortisol concentration. These findings indicated that it is possible to assess stress by measuring salivary cortisol without the need for blood sampling.<br>