Association between salivary and blood hormone concentrations using an automated electrochemiluminescence immunoassay technique: Challenges and pitfalls

Blood-based measures are considered the gold standard for evaluating steroid hormone concentrations, particularly for confirmation of hormone profiles in female-specific research. However, saliva sampling offers several advantages: it can be collected independently by participants, is less invasive and might be a more time- and cost-effective solution. This preliminary study explored associations between salivary and blood plasma hormone (oestrogen, progesterone and cortisol) concentrations using an automated electrochemiluminescence immunoassay technique. Eight healthy, physically active females with a regular natural menstrual cycle provided: (1) daily app-based menstrual tracking data; (2) daily saliva samples; and (3) two blood samples, each at different time points in the third to fifth menstrual cycle estimated using the backward calculation method. Associations between saliva and blood hormone concentrations were analysed using repeated-measures correlations. Progesterone and oestrogen showed positive associations between blood plasma and salivary measures; (r_m= 0.996, p < 0.0001 and r_m= 0.705, p = 0.0507, respectively). Weak non-significant associations for cortisol (r_m= 0.245, p = 0.526) were found. With further work to validate the assay and develop salivary reference ranges, the electrochemiluminescence immunoassay technique might be feasible for use in quantitative determination of progesterone and oestrogen in saliva and have application in research for within-participant monitoring of changes over time.