Anti-doping authorities should abandon a key test used to catch drug cheats because it fails to take into account vital ethnic variations, according to Swiss researchers.
Scientists at Lausanne's anti-doping laboratory claim that tests commonly administered to top-tier athletes to detect testosterone should be replaced by a system that tracks a competitor's biological patterns.
The study, published in the British Journal of Sports Medicine, claims the test is "not fit for purpose". It was funded by Fifa, football's international governing body, and carried out by scientists at the World Anti-Doping Administration (Wada).
Testosterone is a naturally occurring hormone but experts say it is widely used as a steroid in synthetic form to enhance performance among athletes.
Researchers in the French-speaking city examined the testosterone levels of 171 football players in six different countries after steroids were deliberately added to their urine samples.
They reported "significant differences" after performing a chemical analysis of the steroid profiles of 57 Africans, 32 Asians, 50 Caucasians and 32 Hispanics.
The study found levels were naturally highest among Hispanic players, who on average produced marginally more testosterone than Africans and Caucasians and significantly more than Asians.
"Not fit for purpose"
"These results demonstrate that a unique and non-specific threshold to evidence testosterone misuse is not fit for purpose," the study's authors said.
The problem is that ethnic groups have different variations of a gene called UGT2B17, which influences how quickly testosterone is expelled from the body in urine.
Under Wada rules, any ratio of testosterone to epitestosterone greater than 4:1 is considered evidence of possible doping and leads to further tests to look for synthetic testosterone. The normal ratio in healthy males is 1:1.
But the genetic variations skew those ratios. The researchers said the baseline thresholds are actually 5.8:1 for Hispanics, 5.7 for Caucasians, 5.6 for Africans and 3.8 for Asians, the group most likely to secrete the least testosterone into urine.
Wada, which accredits drug-testing labs around the world, said it was "well aware" of the issue of ethnic variations. It said suspicious results are "just one of several warning signals" and are followed up by carbon-isotope tests that are not influenced by genetic factors.
Wada spokesman Frederic Donze also said the agency has been working with the Lausanne lab for more than three years on developing an athlete passport program.
"This approach ... will allow anti-doping organisations to monitor variations in the athlete's biological profile and subsequently target-test or sanction based on abnormal variations," he said.
"This detection strategy is not affected by genetic variations."
The ethnic variations, the study said, make it impossible to apply a universal benchmark for testosterone doping. Scientists instead have called for the introduction of a passport system, which measures variations in individual athletes.
"Even if we apply different thresholds we will not be sensitive enough in the detection of testosterone and we have to use another system," said Christophe Saudan, a researcher with the Lausanne lab. "Now we have to turn to the biological passport, which takes into account the individual range of the athlete.
"The athlete is his own reference. We have to look at the athlete's reference rather than a population reference."
The passport system would measure an athlete's baseline blood and urine profiles against numbers gleaned from subsequent tests. Such "longitudinal" controls wouldn't necessarily look for specific substances, but could detect changes in body chemistry that would indicate use.
Jiri Dvorak, Fifa's chief medical officer, said of more than 25,000 doping tests carried out each year between 2004-08 in world football, just 51 were positive for anabolic steroids. He acknowledged there were ethnic differences.
Dvorak, a member of Wada's health, medical and research committee, said he would submit the study to the panel's next meeting in Montreal, Canada, in September.
The chairman of the IOC's medical commission, Arne Ljungqvist, said the research confirmed what was already known by anti-doping experts but did not cast fresh doubt on previous positive tests.
There have been a number of high-profile cases in sports involving testosterone:
United States cyclist Floyd Landis tested positive with a testosterone/epitestosterone ratio of 11:1 at the 2006 Tour de France. He was later stripped of the Tour title and banned from cycling for two years.
Baseball star Alex Rodriguez admitted using banned substances from 2001-2003 after Sports Illustrated reported that he tested positive for metenolone enanthate and testosterone during baseball's anonymous survey in 2003.
Two Belarusian hammer throwers were stripped of silver and bronze medals from the Beijing Olympics after testing positive for testosterone.
Lausanne and sport
Lausanne is Switzerland's fifth-largest city and is home to the International Olympic Committee since 1915.
It also hosts many of the world's major sports federations as well as Wada's drug testing lab.
Athletes caught taking banned substances can appeal their punishments at the Court of Arbitration for Sport, also in Lausanne.
Following the 1998 Tour de France doping scandal, the Lausanne-based IOC decided to convene a world conference on doping, bringing together all parties involved in the fight against doping.
The conference took place in Lausanne in February 1999 and produced the Lausanne Declaration on Doping in Sport, which provided for the creation of an independent international anti-doping agency to be fully operational for the 2000 Olympic Games in Sydney. The World Anti-Doping Administration (Wada) was established on November 10, 1999. Its headquarters are in Montreal, Canada.
Wada coordinates the development and implementation of the world anti-doping code, the document harmonising anti-doping policies in all sports and all countries. Some 600 sports organisations have signed up to the new code.
The agency focuses on seven areas: code-compliance monitoring; cooperation with law enforcement, science and medicine; anti-doping coordination (ADAMS); anti-doping development; education and athlete outreach.
Since Wada's creation, the number of doping checks has risen from 120,000 to nearly 200,000 a year. About 2% of the tests come back positive.
swissinfo.ch and agencies