The fight against blood doping in sport
Blood doping benefits endurance athletes (notoriously, but not only, cyclists) by raising the red blood cell (rbc) count or haematocrit, and so increasing the oxygen supply to the muscles. It is one of the most difficult types of drug abuse to detect. Awareness of blood doping was raised in the popular press recently when comments were made about the impressive nature of China’s Ye Shiwen’s Olympic gold medal wins and with Lance Armstrong’s (cycling’s famous winner of seven Tours de France after surviving advanced testicular cancer) sudden decision to drop his fight against the US Anti-Doping Agency’s drug charges. Hematocrit levels can be raised by a variety of methods ranging from legal altitude training, to the banned use of autologous blood transfusions and erythropoietin (EPO) injections.
Detection of these banned methods is extremely difficult and the fight against them is being waged in a number of ways. The UCI’s (cycling’s governing body) lines of defence include simply demonstrating possession of banned substances and monitoring hematocrit levels, with a limit set at 50% (normal being 41–50% for men).
Some early success was had with testing urine to distinguish pharmaceutical EPO from the nearly identical natural hormone by isolectric focusing, though its accuracy has been questioned with claims that it is not possible to distinguish pharmaceutical EPO from other unrelated proteins that are present in urine after strenuous exercise or as the result of sample degradation and bacterial contamination.
At present, tests that provide indirect evidence of autologous blood transfusion (where the athlete withdraws and then re-injects his own blood) are under development and involve looking at the ratio of immature to mature red blood cells and might also include the measurement of 2,3-bisphophoglycerate (2,3-BPG). As 2,3-BPG degrades over time, stored blood used for autologous transfusions would have less than fresh blood and so levels of 2,3-BPG lower than normal may then indicate blood doping by this method. The presence of plasticizers in the blood (from the IV bags in which blood is stored) has also been used as evidence of blood doping.
While these advances in the detection of blood doping are being made it is tempting to think that we have got there, that the cheats will be caught. However, in the high-stakes world of elite athletes this would be a naive hope: the possibility of athletes subjecting themselves to EPO gene therapy – so called gene doping – has been suggested and methods for the detection of transgenic DNA following in vivo gene transfer are already being developed.
