The results of two types of tests have thrown Landis’s status into doubt. One of them, a sophisticated measure called a carbon isotope ratio test, will be difficult, if not impossible, for Landis to refute. The test examines the atomic makeup of testosterone in the urine and can determine if it is natural or synthetic.
Landis failed that test, according to a person inside the International Cycling Union with knowledge of the results. Landis’s personal doctor, Brent Kay, confirmed the finding.
Landis said last week that he was expecting the worst because backup samples, or B samples, almost always confirm the initial result. But Kay said the B sample could come back negative.
“The carbon isotope was only mildly elevated,” he said. “We know, from a statistical standpoint, that the first result could have been a false positive.”
The test determines whether the testosterone in the athlete’s urine has less carbon-13 than another naturally occurring hormone in the urine, like cholesterol. The test is considered positive when the carbon isotope ratio — the amount of carbon-13 compared to carbon-12 — is three or more units higher in the athlete’s testosterone than it is in the comparison hormone. It is evidence that the testosterone in the urine was not made by the athlete’s body. Landis’s difference was 3.99, according to his own doctor.
“For me, that would be it,” said Donald H. Catlin, who runs the Olympic drug-testing laboratory at U.C.L.A.
