The term blood doping originally meant doping with blood, i.e. the transfusion of RBCs. RBCs are uniquely suited to this process because they can be concentrated, frozen and later thawed with little loss of viability or activity. There are two possible types of transfusion: homologous and autologous. In a homologous transfusion, RBCs from a compatible donor are harvested, concentrated and then transfused into the athlete’s circulation prior to endurance competitions. In an autologous transfusion, the athlete's own RBCs are harvested well in advance of competition and then re-introduced before a critical event. For some time after the harvesting the athlete may be anemic.
Both types of transfusion can be dangerous because of the risk of infection and the potential toxicity of improperly stored blood. Homologous transfusions present the additional risks of communication of infectious diseases and the possibility of a transfusion reaction. From a logistical standpoint, either type of transfusion requires the athlete to surreptitiously transport frozen RBCs, thaw and re-infuse them in a non-clinical setting and then dispose of the medical paraphernalia.
In the late 1980s an advance in medicine led to an entirely new form of blood doping involving the hormone erythropoietin (EPO). EPO is a naturally-occurring growth factor that stimulates the formation of RBCs. Recombinant DNA technology made it possible to produce EPO economically on a large scale and it was approved in US and Europe as a pharmaceutical product for the treatment of anemia resulting from renal failure or cancer chemotherapy. Easily injected under the skin, pharmaceutical EPO can boost hematocrit for six weeks or longer. The use of EPO is now believed by many to be widespread in endurance sports.
EPO is also not free of health hazards: excessive use of the hormone can cause polycythemia, a condition where the level of RBCs in the blood is abnormally high. This causes the blood to be more viscous than normal, a condition that strains the heart. Some elite athletes who died of heart failure—usually during sleep, when heart rate is naturally low—were found to have unnaturally high RBC concentrations in their blood[1].
[edit] Detection of Blood Doping
A time-honored approach to the detection of doping is the random and often repeated search of athletes’ homes and team facilities for evidence of a banned substance or practice. Professional cyclists customarily submit to random drug testing and searches of their homes as an obligation of team membership and participation in the UCI ProTour. In 2004, British cyclist David Millar was stripped of his world time-trial championship after pharmaceutical EPO was found in his possession. Because athletes sometimes inject or infuse non-banned substances such as vitamin B or electrolytes, the possession of syringes or other medical equipment is not necessarily evidence of doping.
It has also been possible to link athletes to blood doping entirely through documentary evidence, even if no banned substance has been found and no athlete has failed a doping test. The Operación Puerto case is a recent example.
A more modern approach, which has been applied to blood doping with mixed success, is to test the blood or urine of an athlete for evidence of a banned substance or practice, usually EPO. This approach requires a well-documented chain of custody of the sample and a test method that can be relied upon to be accurate and reproducible. Athletes have, in many cases, claimed that the sample taken from them was misidentified, improperly stored or inadequately tested.
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