title: Capillary cortisol sampling during high-intensity exercise.
abstract: Venepuncture is the established "gold standard" for sampling cortisol, but it is expensive, highly invasive and impractical for many experimental and clinical settings. Salivary free cortisol is a non-invasive and practical alternative; however, when cortisol concentrations exceed 500 nmol · L there is a lack of agreement between salivary (free) and venous (bound) cortisol. No known research has assessed whether capillary cortisol accurately reflects venous blood cortisol across a range of concentrations. The objective of the current study was to determine the agreement between capillary and venous blood samples of total plasma cortisol across a range of concentrations. 11 healthy male subjects (26.1 ± 5.3 years) were recruited. Capillary and venous blood samples were collected pre and post (immediately post and post 5, 10, 15 and 20 min) a treadmill VO2max test. Regression analysis revealed a strong relationship (R2=0.96, y=1.0028x + 1.2964 (P<0.05)) between capillary and venous cortisol concentrations. A Bland-Altman plot showed all data was within the upper and lower bounds of the 95% confidence interval, and no systematic bias was evident. In conclusion, capillary sampling is a valid technique for measuring bound cortisol across a range of concentrations.
authors.affiliation: School of Sciences and Physical Education, University of Canterbury, Christchurch, New Zealand. simon.fryer@pg.canterbury.ac.nz
authors.forename: S
authors.initials: S
authors.lastname: Fryer
authors.forename: S
authors.initials: S
authors.lastname: Hillier
authors.forename: T
authors.initials: T
authors.lastname: Dickson
authors.forename: N
authors.initials: N
authors.lastname: Draper
authors.forename: L
authors.initials: L
authors.lastname: Stoner
authors.forename: D
authors.initials: D
authors.lastname: Winter
authors.forename: J
authors.initials: J
authors.lastname: Young
authors.forename: L
authors.initials: L
authors.lastname: Cohen
mesh_terms: D000328:Adult; D002196:Capillaries / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011677:Punctures; D012044:Regression Analysis; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry / Q000502:physiology; D014680:Veins / Q000502:physiology*; D055815:Young Adult
chemical_list: D006854:Hydrocortisone