Int J Sports Med 2012; 33(10): 842-845
DOI: 10.1055/s-0032-1311584
Clinical Sciences
© Georg Thieme Verlag KG Stuttgart · New York

Capillary Cortisol Sampling during High-Intensity Exercise

S. Fryer
1  School of Sciences and Physical Education, University of Canterbury, Christchurch, New Zealand
,
S. Hillier
2  Emergency Medicine, Tauranga Hospital, Tauranga, New Zealand
,
T. Dickson
1  School of Sciences and Physical Education, University of Canterbury, Christchurch, New Zealand
,
N. Draper
1  School of Sciences and Physical Education, University of Canterbury, Christchurch, New Zealand
,
L. Stoner
3  School of Sport and Exercise, Massey University, Wellington, New Zealand
,
D. Winter
1  School of Sciences and Physical Education, University of Canterbury, Christchurch, New Zealand
,
J. Young
4  Lipid and Diabetes Research Group, Diabetes Research Institute, Christchurch, New Zealand
,
L. Cohen
5  Emergency Medicine, Christchurch Hospital, Christchurch, New Zealand
› Author Affiliations
Further Information

Publication History



accepted after revision 07 March 2012

Publication Date:
16 May 2012 (online)

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.