Racial differences turn out to cause misleading results in a standard screening test for steroids. This may mean that sportspeople from certain ethnic groups are less likely to be caught if they cheat.
Tests on urine samples from soccer players of six nations have shown that results are muddled by a genetic factor linked to race.
The tests in question, which were introduced by the in 2004, measure how much of the male hormone testosterone is in a urine sample compared with its close relative, epitestosterone.
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If there is more than four times as much testosterone 鈥� a 鈥淭/E ratio鈥� of 4 or more &ndash this is taken as preliminary evidence that the athlete has cheated by injecting extra testosterone. The sample can then be sent for further analysis to confirm that cheating took place.
Drug excreted slowly
Now researchers in Switzerland have shown that people in some racial groups, particularly east Asians, frequently have a variant of the UGT2B17 gene which means that they take longer than others to excrete testosterone, so testosterone levels in their urine stay low.
鈥淚t means that some athletes can use testosterone without raising the T/E ratio above 4,鈥� says lead researcher Christophe Saudan of the in Epalinges, near Lausanne.
In other racial groups, including black Africans and Caucasians, the gene variant is much rarer, so most people from these groups excrete testosterone more efficiently. This makes them more likely to be caught by the current test if they have cheated.
Deliberate doping
Saudan and his colleagues discovered the misleading results of the test by analysing the background steroid profiles from 171 soccer players. The players came from Argentina, South Africa, Uganda, Japan, Italy and Switzerland, and represented four groups: Africans (57), Asians (32), Caucasians (50), and Latin-American (32).
When the researchers applied the tests, they found that the Asians, 81 per cent of whom had the gene variation that made them excrete testoserone slowly, usually fell below the T/E threshold of 4.
On the basis of their results, they recalculated test thresholds that would be fair for each ethnic group, which worked out as 3.8 for Asians, 5.6 for Africans, 5.7 for Caucasians and 5.8 for Latin-Americans.
Athlete鈥檚 passport
Saudan says the solution is to introduce , which would use each athlete鈥檚 individual metabolic profile as a baseline against which to monitor for any deviations suggesting cheating, such as exceptionally high concentrations of red blood cells.
鈥淚t means that each athlete would act as their own reference,鈥� says Saudan, allowing the authorities to monitor for suspicious deviations from an athlete鈥檚 own baseline characteristics.
Despite his latest results, Saudan says that the T/E test should not be dropped, since further tests are always needed to prove guilt. 鈥淚t鈥檚 only a filter to select suspicious samples,鈥� he says. More expensive tests using a technique called isotopic ratio mass spectrometry are then used to confirm cheating.
Warning signal
A spokesman for WADA agrees, saying that the agency is 鈥渨ell aware鈥� of the phenomenon identified by Saudan. 鈥淭he T/E ratio is just one of several warning signals that can lead to further action by anti-doping laboratories,鈥� he told New 杏吧原创.
The spokesman also confirmed that work is well under way to develop the 鈥渁thlete鈥檚 passport鈥� concept, including programmes with Saudan鈥檚 own lab. 鈥淲e鈥檝e already started working with them on the development of an endocrine module for the athlete passport, which will include longitudinal follow-up of steroid profiles.鈥�
Saudan himself says that such tests would enable cheating to be tracked and detected, even in those athletes whose genetic profile makes it likely that they will escape detection by the current screening test.
Journal reference: , DOI: (in press)
