S HORT RE P ORT Comparison between ECL and ELISA for the detection of salivary cortisol and determination of the relationship between cortisol in saliva and serum measured by ECL

ABSTRACT: Salivary cortisol has been increasingly used as a stress biomarker since saliva sampling induces less additional stress than blood sampling. Enzyme-linked immunosorbent assay (ELISA) has been commonly used to measure salivary cortisol in stress related research. Recently, electrochemiluminescence (ECL), a routine immunoassay analyser, has been suggested to measure salivary cortisol. Therefore, the aims of this study are: (1) to compare salivary cortisol level measured by ELISA and ECL and (2) to determine the relationship between salivary cortisol and serum cortisol measured by ECL. Both salivary and serum samples were collected from 83 volunteers for cortisol measurement by ECL analysis. The salivary cortisol value was 3% of that of the serum cortisol. For ECL, the positive correlation between salivary and serum cortisol levels was significant (r = 0.84; p < 0.001). The measurement by two different methods did not show any significant difference (p = 0.5497). The correlation of salivary cortisol values measured by both techniques was significant (r = 0.81; p < 0.001). The result suggests that ECL seems to be more practical and cheaper for salivary cortisol measurement