Blood doping
From Freepedia
Blood doping is the practice of illicitly boosting the number of red blood cells (RBCs) in the circulation in order to enhance athletic performance. Because they carry oxygen from the lungs to the muscles, more RBCs in the blood can improve an athlete’s aerobic capacity and stamina. RBC concentration is commonly expressed as hematocrit, which is the fraction of blood cells that are RBCs. A normal hematocrit in adult men is 42-48%. In women, hematocrit is typically five percent lower.
Methods
The term blood doping originally meant literally doping with blood, i.e. the transfusion of RBCs. In a homologous transfusion, RBCs from a compatible donor are harvested, concentrated and then transfused into the athlete’s circulation prior to competition. RBCs are uniquely suited to this process because they can be concentrated, frozen and later thawed with little loss of viability or activity. In an autologous transfusion, the athlete harvests his own RBCs well in advance of competition and then re-introduces them before a critical event. For several weeks 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 such as professional bicycle racing.
EPO is also not free of health hazards: excessive use of the hormone can produce so many RBCs that the blood becomes abnormally viscous and strains the heart. Some elite athletes who died of heart failure—usually in their sleep—were found to have had hematocrits of 60% or more.
Testing and Enforcement
Blood doping figures prominently in the cat-and-mouse game between doping athletes and sports authorities, but blood doping is much more difficult to detect than, for example, the use of anabolic steroids. One approach, taken by the Union Cycliste Internationale (UCI) has been to impose a 15-day suspension from racing on any male athlete with a hematocrit above 50%. A few athletes have normally high hematocrit, which they must demonstrate through a series of consistently high samples over an extended period of time.
Some success has also been realized in developing specific tests to detect transfusions and EPO use. In 2000 a test was introduced that can detect pharmaceutical EPO by distinguishing it from the nearly-identical natural hormone. It is of limited use, however, since the pharmaceutical EPO disappears from the circulation within a few days of administration even though its effects can last for months. The test method, which relies on a scientific technique known as gel electrophoresis, has also been criticized as subjective in the interpretation of results. In 2004, British cyclist David Millar was stripped of his world time-trial championship because of EPO use but the charge was based on his possession of pharmaceutical EPO rather than on a positive blood test. 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.
Also in 2000, a test was introduced to detect homologous blood transfusions based on a technique known as fluorescent-activated cell sorting. By examining markers on the surface of blood cells, the method can determine whether blood from more than one person is present in an athlete’s circulation. The American cyclist Tyler Hamilton failed this test during the 2004 Olympics but was allowed to keep his gold medal because of irregularities in the processing of his sample. He is appealing another positive test for homologous transfusion to the International Court of Arbitration for Sport, asserting both that the test method is unproven and that he is one of a small number of chimeric humans having more than one population of blood cells.
At present there is no way of detecting autologous transfusions but scientific researchers and the World Anti-Doping Agency (WADA) have promised that a test will eventually be introduced.
