Detecting EPO in athletes is a difficult test

How easy is it to catch athletes who use EPO?

Not very. Currently, the most widely used method to detect EPO [erythropoietin, a hormone] is a urine-based test introduced at the 2000 Summer Olympic Games in Sydney, Australia. In 2003, a report commissioned by the World Anti-Doping Agency concluded that the test was valid, and since then the agency has accredited 33 labs to administer it.

Although the agency continues to call the test "valid and reliable," the results of a Danish study published in June in the online edition of the Journal of Applied Physiology imply that the test is far from foolproof.

Eight male non-athlete volunteers were injected every other day for two weeks (the "boosting period") and then every seven days for two weeks (the "maintenance period"). Urine samples were sent to two accredited labs during these four weeks and afterward. At Lab A, 100% of the samples tested positive during the boosting period; 37.5% tested positive and 12.5% were considered suspicious during the maintenance period; and 8.3% tested positive and 12.5% were considered suspicious during the post-treatment period. But in testing identical samples, Lab B didn't find any positives.

The test was designed to detect the so-called first generation of EPOs. But two later generations -- developed to have longer-lasting effects -- are already on the market. Before the Tour de France expulsions, it was widely believed that no tests were yet in use for detecting these newer drugs.

But the riders who got the boot were caught using CERA, or continuous erythropoietin receptor activator, a third-generation drug that only became available in Europe at the start of the year. (Though it has also been approved for use in the United States, it's not being sold here yet because of patent disputes.)

CERA employs polyethylene glycol, a chemical that makes the drug longer-lasting, but also "bigger," because polyethylene glycol molecules are relatively large. In fact, rumor once had it that the drug was too big at the molecular level to squeeze its way into the kidneys, meaning a urine-based test could never detect it -- a rumor that seems to have bitten the dust.

In a report on Cyclingnews.com, a spokesman for the anti-doping agency said it worked with Roche Pharmaceuticals, CERA's manufacturer, to develop a test before the drug went on sale.

In a further testing complication, first-generation EPOs continue to enhance performance after they are no longer detectable. One published report found detection to be difficult just three days after injection. In the Danish study some detection did occur outside the three-day window. On the other hand, many false negatives occurred within the window. And overall, throughout the post-treatment period, the men continued to perform better than their pre-injection baseline -- in workouts on stationary bicycles -- although across the two labs only two of their 48 samples (less than 5%) tested positive.

The study authors report that over the years, accredited labs have analyzed more than 2,600 samples and found only nine positives. (These figures do not include the recent Tour de France tests. Also, the anti-doping agency says it has refined its methods since 2005.) These figures could imply that few athletes use EPO, the study authors note. But instead they conclude, based on their data, that athletes can use EPO "without great risk" of being caught.