Background: Cortisol, cortisone and the ratio of cortisol to cortisone in saliva, urine and hair are acute, short-term and long-term biomarkers to reliably assess the activity of hypothalamic-pituitary-adrenal (HPA) axis and 11β-hydroxysteroid dehydrogenase (11β-HSD). One key issue is whether these biomarkers have intraindividual relative stability. Salivary, urinary and hair cortisol was proven to show considerable long-term intraindividual relative stability. However, currently unknown is whether cortisone and the ratio in saliva, urine and hair show intraindividual relative stability.
Methods: The present study utilized a longitudinal design to validate long-term stability within two weeks of three biomarkers in saliva and urine, and long-term stability within twelve months of three hair biomarkers. Salivary, urinary and hair steroids were measured with high performance liquid chromatography tandem mass spectrometry.
Results: Three biomarkers in urine and hair showed moderate test-retest correlations with coefficient (r) ranging between 0.22 and 0.56 and good multiple-test consistencies with coefficient of intraclass correlation (ICC) ranging between 0.42 and 0.67. Three single-point salivary biomarkers showed weak to moderate test-retest correlations (r's between 0.01 and 0.38) and poor to fair multiple-test consistencies (ICC's between 0.29 and 0.53) within two weeks. Three single-day salivary biomarkers showed moderate test-retest correlations (r's between 0.23 and 0.53) and good multiple-test consistencies (ICC's between 0.56 and 0.66) within two weeks.
Conclusions: Three biomarkers in urine and hair showed moderate long-term intraindividual relative stability. Three single-point salivary biomarkers showed weak to moderate short-term and long-term intraindividual relative stability, but three single-day salivary biomarkers showed moderate short-term and long-term intraindividual relative stability.
Keywords: 11β-Hydroxysteroid dehydrogenase; Cortisol; Cortisone; Intraindividual stability; Tandem mass spectrometry; The ratio of cortisol to cortisone.
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