Blood, sweat and gears — the race against erythropoietin use in cycling
Doping in sport, in particular cycling, has been doing its rounds in the media again. Sadia Naeem takes a look at the use of erythropoietin and how to detect drug cheats
In January, US cyclist Lance Armstrong ended a decade of persistent allegations and vehement denial by admitting that he used performance-enhancing drugs to power him to seven consecutive Tour de France victories. But one question remained. Just how did Armstrong beat the testers for so long? How can he have not turned up a single positive test in his 11-year career?
The US Anti-Doping Agency’s report1 into the US Postal Service team, which Armstrong competed for from 1999–2005, exposed the collaborative involvement of not only Armstrong but the entire USPS team of riders, doctors and trainers, as outlined in more than 200 pages of damning evidence. What is perhaps more worrying than the variety of drugs now used is the increasingly sophisticated pharmacological manipulation used to evade drug tests.
EPO and its administration
The typical drugs used in sport were all present in the report, including erythropoietin (EPO). EPO is used to boost endurance by stimulating red blood cell (erythrocyte) production, thus increasing the body’s oxygen-carrying capacity. It is also used to treat anaemic renal failure patients. According to the report, the cyclists injected EPO intravenously on the advice of team doctors, who knew that clearance following intravenous administration was faster than following subcutaneous, the usual administration method.
According to one study, the half-life of erythropoietin is approximately three times longer for subcutaneous administration than for intravenous,2 while another reported mean half-lives of four-and-a-half and 25 hours following intravenous and subcutaneous administration,3 respectively. Additionally, higher peak levels are achieved faster following intravenous administration. EPO detection windows can therefore effectively be bypassed by intravenously injecting during evenings.
EPO’s effect on haematocrit
Centrifuges and Hemocue monitors were used by the team to monitor the riders’ haematocrit — the percentage of erythrocytes in the blood — and haemoglobin concentration, respectively. On discovering a high haematocrit, only 20 minutes were required for an infusion of 500–1,000ml of 0.9 per cent saline to dilute the blood and increase the fluid volume, thereby decreasing the ratio of erythrocytes to fluid and thus the haematocrit to a test-passing level. The effect could be retained as long as the cells survived. This could be up to three months, the typical lifespan. Needless to say, along with EPO, saline is on the World Anti-Doping Agency’s (WADA) Prohibited List.
Such manipulation was deemed necessary when the Union Cycliste Internationale, cycling’s governing body, introduced a rule in 1998 that prevented riders with a haematocrit above 50 per cent from racing (normal haematocrit values for men and women is about 40–50 per cent and 36–46 per cent,4,5 respectively).
What is the rationale for the rule? EPO, like any drug, has health risks. An athlete with a haematocrit exceeding 50 per cent is prohibited from racing because the blood becomes more viscous as the ratio of erythrocytes to plasma increases, potentially leading to circulation problems, hypertension, thrombosis, heart attacks and stroke. The danger is particularly high during sleep when the heart rate slows down, as reflected by the death of Belgian cyclist Johan Sermon in his sleep. He was suspected of EPO abuse, in 2004. In the past decade,6 as well as the 1980s, there were a number of elite cyclist deaths from heart attacks attributed to EPO.
Testing for EPO
The tests for EPO have become more robust over the years. But with potentially over 100 undetectable, structurally different EPO variants,7 they have nowhere near the sensitivity or accuracy required to detect EPO in athletes who are, it seems, always one step ahead.
The International Olympic Committee debuted a validated testing method at the 2000 Sydney Olympics involving a combination of blood testing for initial EPO detection and urine testing for confirmation. Only if an athlete failed both tests would they be penalised.
The urine test involves the process of isoelectric focusing — the separation of protein mixtures according to their charge — followed by immunoblotting for identification of the compounds. Although deemed the most conclusive of the two,8 the urine test has its flaws. Athletes have been known to stop using EPO up to a week before a competition begins, safe in the knowledge that EPO will have passed out of their system while the effects are retained. Some may additionally use blood doping: removing units of blood while the number of erythrocytes is high and replacing it closer to competition time means the benefit of higher oxygen-carrying capacity is regained while EPO levels will have reduced.
The current WADA-accredited tests have also been subject to doubt and insinuations that they may be unfit for purpose, with one study reporting significant differences between two laboratories’ EPO test results.9 This apparent downfall is highlighted by successful court challenges to positive tests, including that of Belgian triathlete Rutger Beke, who was exonerated after being suspended from competition in 2004.
Come 2007, the biological passport programme was introduced, which aimed to collect information from blood and urine samples over time in order to create a baseline for which to compare test results with. Although considered the most robust of all testing programmes, even it may not detect chronic EPO abuse by athletes who begin using EPO before initial sample collection.
The evolvement of EPO use over the years has resulted in the relatively new practice of microdosing, a method now known to elude urine testing and the biological passport programme, whereby athletes inject smaller doses of EPO more frequently. Microdosing seems to increase blood volume and mask other markers in the blood,10 thereby roughly maintaining the haematocrit. Again, detection is extremely difficult.
It is clear that, in the grimy world of EPO use in sport, corrupt athletes are currently ahead of the testers. Fierce competition, money and stakes are all evident in “the greatest race on earth” and it appears that simply testing for drugs in and out of competition may not be enough in the near future, no matter how technical the tests are.
1 Reasoned decision of the United States Anti-Doping Agency on disqualification and ineligibility. Colorado Springs (CO): United States Anti-Doping Agency; 2012 Oct 10. Available at: http://cyclinginvestigation.usada.org (accessed 10 February 2013).
2 Hayashi N, Kinoshita H, Yukuwa E et al. Pharmacokinetic analysis of subcutaneous erythropoietin administration with nonlinear mixed effect model including endogenous production. The British Journal of Clinical Pharmacology 1998;46:11–19. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1873985/ (accessed 10 February 2013).
3 Salmonson T, Danielson B G, Wikstrom B. The pharmacokinetics of recombinant human erythropoietin after intravenous and subcutaneous administration to healthy subjects. The British Journal of Clinical Pharmacology 1990;29:709–13. Available at: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2125.1990.tb03692.x/abstract (accessed 10 February 2013).
4 MedlinePlus. Bethesda (MD): National Library of Medicine (US); Hematocrit; [updated 2013 Jan 24, accessed 2013 Feb 10]. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/003646.htm.
5 O’Leary MF, Wheeler TM. Hematocrit. Medscape reference; 2012. Available at: http://emedicine.medscape.com/article/2054320-overview (accessed 10 February 2013).
6 Henderson C. Pantani death raises questions. London: British Broadcasting Corporation (BBC). 18 April 2004. Available at: http://news.bbc.co.uk/sport1/hi/other_sports/cycling/3495967.stm (accessed 10 February 2013).
7 Velonation Press. Anti-doping scientists warns of undetectable EPO variants. Velonation; 16 March 2012. Available at: http://www.velonation.com/News/ID/11385/Anti-doping-scientist-warns-of-undetectable-EPO-variants.aspx (accessed 13 February 2013).
8 Questions and answers on EPO detection. Montreal: World Anti-Doping Agency (WADA); 2011. Available at: http://www.wada-ama.org/en/Resources/Q-and-A/EPO-Detection/ (accessed 10 February 2013).
9 Lundby C, Achman-Anderson NJ, Thomsen JJ et al. Testing for recombinant human erythropoietin in urine: problems associated with current anti-doping testing. Journal of Applied Physiology 2008;105:417–9. Available at: http://jap.physiology.org/content/105/2/417.long (accessed 13 February 2013).
10 Austen I. Cyclists find new method for using old doping tool. New York: The New York Times; 25 May 2010. Available at: http://www.nytimes.com/2010/05/26/sports/cycling/26micro.html?_r=0 (accessed 10 February 2013).
Sadia Naeem is a hospital preregistration trainee and blogger for PJ?Online
Citation: The Pharmaceutical Journal DOI: 10.1211/PJ.2013.11118082
Recommended from Pharmaceutical Press
An innovative book which presents statistics in the context of clinical trials conducted during pharmaceutical drug development.£38.00Buy now