Hamilton's defence: The vanishing twin?

By Susan Westemeyer, with additional reporting from Cyclingnews staff

With a verdict in the Tyler Hamilton blood doping case expected today (Monday), information has already started to leak out about the likely outcome of the case, and the nature of Hamilton's defence. In an article in the Los Angeles Times, it appears that the "vanishing twin theory" is being used to try to explain the mixed blood cell population in Hamilton's body. "A theme central to Hamilton's defence is the notion of a 'vanishing twin' who shared the womb when Hamilton was a fetus - a point on which there is much speculation but no proof," wrote the LA Times, which said it had "obtained key documents before the arbitration panel, including legal briefs, test results, and the transcript of the hearing six weeks ago where the U.S. Anti-Doping Agency and Hamilton's defense team presented their cases." These documents likely did not come from the UCI or the USADA, who typically don't release these to the media.

The newspaper also released specific numbers for Hamilton's blood tests last spring. Riders are not be allowed to start a race if they receive a score of more than 133 in the Stimulation Index, a simple formula for profiling blood cell growth that takes into account haemoglobin and reticulocytes (immature blood cells). An explanation of the formula can be found in the footnote of Cyclingnews' Anti-doping measures get tougher article, published in July last year.

The average SI score for professional cyclists is 90. At Liege-Bastogne-Liege last year, Hamilton scored 123.8. It was up to 132.9 the next week by the Tour de Romandie, and with it came a hematocrit level of 49.7% (the UCI's nominal limit is 50%) and a reticulocyte index of 0.22 (which is below normal limits). Hamilton claimed that both the hematocrit test and the reticulocyte index taken at Romandie were inaccurate.

These readings caused the UCI to inform Hamilton that "he was going to be watched because his 'blood values showed strong signs' of 'a possible manipulation,'" according to both the LA Times and articles in L'Equipe in 2004. The warning letters that Hamilton received were like a red card in football.

Testimony given at Hamilton's hearing by Australian scientist Ross Brown said that "only reasonable explanation" for Hamilton's blood values was that he had undergone one, and possibly two transfusions: one near the start of 2004, and perhaps another in June or July, with the occasional "top up". At the hearing, Hamilton denied that he had had multiple transfusions.

In Hamilton's defence, both the chimera (naturally occurring mixed blood cells) and 'vanishing twin' argument was put forward by David Housman, a genetics expert and MIT professor, who presented expert testimony. He claimed that cells can transfer from one to unborn twin to another in the womb, "and bone marrow cells can persist for life." Both USADA and WADA have dismissed this theory, which could be easily verified by further testing on Hamilton.

Hamilton's lawyer Howard Jacobs suggested in the hearing that there were problems with the test, one being that it "doesn't produce an objective standard", i.e. there is either a mixed blood cell population or there isn't - there are no percentages; and the other being that it doesn't prove that the subject had a blood transfusion, only that there was a mixed blood cell population present. This raises the question of other things, such as the 'vanishing twin' or human chimera theories, that might cause false positives.

No Georgia

Whatever the verdict, it's highly unlikely that Hamilton will race in the Tour de Georgia - for Phonak or any other team. Hamilton was sacked by Phonak last year and has yet to sign for a new team. According to UCI rules, he would need to have done this at least three days before the start of a race in order to be present on their team roster, even as a reserve. In addition, the UCI would have to approve his inclusion on a team.

Phonak's press officer Georges Lüchinger told Cyclingnews that he did not know whether Hamilton would ride in Georgia, nor if Hamilton would win his case. If Hamilton is cleared, or is given a sanction of less than two years, then Cyclingnews understands that the UCI will certainly appeal the decision.

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