Agreement of steroid profiles in Athlete Biological Passport residues and corresponding serum samples.

The steroid module of the Athlete Biological Passport (ABP) is based on the analysis of six endogenous steroids in urine samples and a Bayesian statistical approach. However, the urinary steroid concentrations may be affected by confounders like microbial degradation, possible co-administration of diuretics as masking agents, insufficient conjugate hydrolysis or UGT2B17 gene polymorphisms affecting glucuronidation. Therefore, it can be helpful to use other matrices (ABP blood and serum samples) to quantify steroids and thereby support noticeable deviations in the Athlete Biological Passport, for example, abnormally increased urinary testosterone/epitestosterone (T/E) ratios. Aim of the study was to investigate the feasibility to re-use plasma obtained from athlete ABP blood samples for measuring a steroid profile. Therefore, testosterone, androstenedione, cortisol and cortisone were quantified in 36 intra-individual matching ABP blood and serum samples. The steroid levels measured in both matrices showed a high agreement indicating a good stability uninfluenced by storage temperature and duration. Our results pointed out the possibility to expand the athlete ABP blood analysis for steroid profiling.