I.2.3 Although a single blood Sample is sufficient within the f ramework of the hematological module of the  Athlete Biological Passport , it is recommended to collect an additional (B) Sample for a possible subsequent analysis of Prohibited Substances and Prohibited Methods in whole blood (e.g., detection of homologous blood transfusion (HBT) and/or  erythropoietin receptor agonists  (ERAs) ).