Comparing the Stability and Detectability of Testosterone Esters in Capillary Serum, Sodium Fluoride‐Containing Plasma, and Dried Blood Spots After Testosterone Ester Administration

Steroid esters are a frequently used ergogenic aid among athletes, and their direct detection represents an important approach to anti-doping efforts. However, the presence of esterase enzymes in blood complicates these efforts. Although dried blood spots (DBS) have emerged as a promising solution to the esterase problem, the limited sample volume creates both analytical and practical challenges. The larger collection volume for liquid blood may allow for higher analytical sensitivity, thus offsetting the effects of esterase activity in practical scenarios. First, to evaluate the effects of blood esterases ex vivo, 10 individuals were administered a single dose of either testosterone propionate or testosterone cypionate. Venous blood was collected into serum separator tubes (SST) serum and NaF-containing tubes and stored at varying conditions. Both esters significantly decreased in serum while no ester loss was observed in the NaF-containing plasma. Next, to compare the detectability across matrices stored at conditions meant to mimic real-world scenarios, the individuals administered testosterone propionate collected capillary serum, capillary NaF-containing plasma, and capillary DBS at various times postadministration. Each sample type was stored at different conditions designed to mimic what may be encountered during real-world shipping scenarios. Similar detectability of testosterone propionate was observed between all NaF, DBS, and SST samples stored under cool conditions, whereas detectability was better in NaF and DBS samples under ambient and warm conditions. These results indicate that for samples not shipped in temperature regulated conditions, DBS and NaF-containing plasma are the preferred matrices.