Blood Doping in Sports and New Testing Methods for Detection

Blood doping is the practice of intravenous infusions of blood or use of a recombinant peptide hormone called erythropoietin (EPO) in order to increase athletic performance. It works by increasing total aerobic reserve by increasing transport of oxygen to muscles being worked. This stimulates not only the amount of oxygen transported, but also maximizes the oxygen used.

Blood doping is popular among cyclists, skiers, runners, and others engaged in heavily aerobic sports who seek a competitive edge though it is illegal. The athletes either use autologous or non-autologous blood for the transfusions. Autologous blood refers to their own blood, while non-autologous is donor blood.

With non-autologous doping, the major antigens of the ABO groups have to be a match with the athlete, but the minor antigens aren't as crucial to match. When EPO was first introduced as an anemia drug in the '80s, blood transfusions were largely abandoned, especially non-autologous ones, because of the risk of contracting bacterial and viral infections, or having a deadly immune reaction. With the advent of a reliable test for EPO, blood transfusions resurged in popularity.

At least four weeks before the competition, but up to eight weeks before, blood is collected from the athlete themselves if they opt for autologous transfusion. The red blood cells (RBCs) are separated from plasma and stored for transfusion via glycerol freezing. This is to preserve the erythrocytes and is critical if storage is longer than three weeks. Upon thawing, the RBCs are transfused into the athlete one to seven days before (s)he is due to compete.

Most athletes prefer to use their own blood for two reasons. The first is risk of contamination from donors. The second reason has to do with competition. Blood doping is grounds for disqualification if the competitor wins. It is more difficult to detect blood doping if there is only one type of blood in the body -- the host's. Only blood tests that look for physiological changes in the blood after transfusion are capable of detecting blood doping for certain. Other methods used to determine if blood doping has occurred include looking for an elevated level of soluble transferring receptor in serum, which indicates use of EPO.

Sports officials are making a concentrated effort to crack down on blood doping, the use of EPO, and other illegal methods employed to enhance performance. Blood doping and EPO were initially popular because it was almost impossible to detect their use when the only tests performed were urine screenings. Blood testing is the obvious answer for detecting these practices, and the International Olympic Committee has now instituted a policy of testing both the urine and blood of their Olympic competitors.

The new methods of testing detect both EPO use and recent blood transfusions. The test for detecting blood doping is antibody-based. It detects foreign cells within the blood sample, because RBCs from an individual have the same set of proteins and antigens. The blood test employed is more effective for detecting non-autologous transfused blood. It detects fifteen different minor antigens. Several sets of antigens indicate blood from at least two people in the same person.

However, those who think their own blood will not be detected are wrong. It can detect changes that inevitably occur to stored blood that is re-transfused. Currently, the only way around this is for athletes to give themselves an infusion of their own blood right before competing.

In the world of cycling, a recent scandal surprised fans and competitors alike. Tyler Hamilton, winner of a gold medal at the Athens Olympics, tested positive for blood doping during the Tour of Spain. He denied any wrongdoing, claiming the flaw was with the test. The creator of the test, Michael Ashenden, responded, "The test doesn't make mistakes. You either have someone else's blood in your circulation or not."

But there are three circumstances that could cause a false positive on Ashenden's test. If a competitor had a recent bone marrow or stem cell transplant, they would test positive for blood doping. This would be easy to verify and wouldn't disqualify the athlete. The second scenario could only occur with someone who has a non-identical twin. Sometimes, twins exchange blood in utero, leaving both with two types of blood in their bodies. The third circumstance can't be proved or disproved at this time. If two embryos fused together in the womb, the resulting person could be chimeric, meaning they have two blood types circulating. This is extremely rare, but is the defense Hamilton chose. There is confusion as to why he would fail the test at the race, but pass weeks later, since a chimeric person would always fail.

Sports officials are trying to clean up sporting competitions and eliminate cheating. The new blood test offers promising results to reduce the number of blood dopers, though it still faces challenge in the courts. Many athletes protest having to take a blood test. "No one is forced to compete," says Prince Alexandre de Merode, head of the International Olympic Committee's medical commission. "We have our rules, and it is also in the constitution that they must take the test. If they don't, they are out."