Is blood blood? Comparing quantitation of endogenous steroids and luteinizing hormone in concurrently collected venous serum and Tasso+ SST capillary serum samples.

The monitoring of endogenous steroids in urine has been an important component of the Athlete Biological Passport (ABP) for the last decade. Recently, the quantitation of endogenous steroids in blood has been incorporated into the ABP to increase sensitivity in circumstances where the excretion of urinary ABP biomarkers is low. Current ABP guidelines mandate the use of venous blood draws for blood steroid sample collections, however, recent efforts have focused on investigating the use of less invasive sample collection methods, such as capillary blood collected from the upper arm. The focus of this study was to compare the analytical results of venous and capillary blood collected weekly from 20 individuals, 10 males and 10 females, over six weeks. The two primary biomarkers of the blood steroid ABP module, testosterone (T) and the testosterone/androstenedione (T/A4) ratio, were compared, as well as luteinizing hormone (LH) and the T/LH ratio in male participants, two biomarkers known to be responsive to T use. All biomarkers showed excellent agreement between venous and capillary blood. Longitudinal stability between sample types within individuals was also comparable for all biomarkers. Finally, storage of simultaneously collected capillary samples at room temperature and frozen conditions was compared with evaluate the potential impact of non-cold chain shipping conditions. Most biomarkers showed excellent agreement between frozen and room temperature storage conditions. These results indicate capillary blood collections represent a promising alternative to venous blood collections for the blood steroid module of the ABP.