A Comparison of Capillary, Venous, and Salivary Cortisol Sampling after Intense Exercise

Abstract

Venipuncture is expensive, invasive, and impractical for many sport-science and clinical-based settings. Salivary free cortisol is often cited as a noninvasive practical alternative. However, when cortisol concentrations exceed the corticosteroid-binding globulin (CBG) point of 500 nmol/L, a lack of agreement between salivary and venous blood cortisol has been found. Alternatively, capillary blood may present a minimally invasive, cost-effective, and practical surrogate for determining cortisol concentration.Purpose:The aim of this study was to determine whether cortisol concentrations sampled from capillary blood and saliva accurately reflect those found in venous blood across a large range of concentrations after intense exercise.Methods:Eleven healthy aerobically trained male subjects were recruited. Capillary, salivary, and venous blood samples were collected before and after (immediately and 5, 10, 15, and 20 min after) a treadmill VO2 max test.Results:Capillary and venous concentrations increased at a similar rate after exercise (Cohen d.14–.33), increasing up to 15 min postexercise before a decline was seen. Salivary cortisol values increased at a slower rate than venous and capillary cortisol but continued to increase 15 min postexercise (Cohen d .19–.47 and .09–.72, respectively).Conclusions:Capillary cortisol accurately reflects concentrations assayed from venous blood across a range of values below and above the CBG binding point. Capillary sampling provides a minimally invasive, cost-effective, practical surrogate for assessment of hypothalamic-pituitary-gland function.

Salivary but not plasma cortisone tracks the plasma cortisol response to exercise: effect of time of day

“…Broad range correlations (r = 0.35 to r = 92) between salivary and plasma/serum cortisol during and following exercise have been reported [5,7,11,17,22]. Our correlations between plasma and salivary cortisol induced by exercise were significant in the PM (r = 0.81) and the AM (r = 0.61), but the difference did not reached significance (p = 0.10).…”

“…More recently, Fryer et al [11] extended this line of work by conducting validation studies between plasma derived from finger stick and venous sampling, along with salivary sampling. The capillary blood sampling method that follows was a modified version of Fryer's and associates [11] work. The subjects were seated in a quiet room, and their hand was heated for 3-5 min; 300-500 µl blood samples were collected via finger prick with a Safety Lancet 1.8 mm × 18G Extra (Sarstedt, Newton, NC) into a capillary blood collection tubes Microvette CB300 and Microvette 500, both coated with lithium heparin (Sarstedt, Newton, NC).…”

“…The use of paired capillary blood and salivary sampling to assess glucocorticoid correlations in exercise studies was first reported by Port [17]. More recently, Fryer et al [11] extended this line of work by conducting validation studies between plasma derived from finger stick and venous sampling, along with salivary sampling. The capillary blood sampling method that follows was a modified version of Fryer's and associates [11] work.…”

“…Samples were collected at baseline, 5 min Post (Post-EX5), and 20 min Post-EX (Post-EX20); these two time points would capture significant increases in hormone concentration [9,11]. The use of paired capillary blood and salivary sampling to assess glucocorticoid correlations in exercise studies was first reported by Port [17].…”

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“…Fingerprick sampling and capillary tubes may be a viable alternative due to the relatively small volume of serum required for analysis and therefore less apprehension than during venous blood collection. Capillary TC accurately reflects samples from venous blood [55], yet further investigation is required as to whether this is a viable technique for testosterone measurement. An often cited relationship exists between T and aggression, which is further demonstrated by the reported increased aggression or 'roid-rage' following consumption of supraphysiological dose T in anabolic androgenic steroid users (AAS).…”