Cut and paste from my post in this thread, related to the subject.http://www.dailypelotonforums.com/main/ind...ost&p=31884
3. "Best metabolite" (5bA) and the differences in Floyd's 5aA and 5bA.
Jacobs asserted that based on his research delta C13 difference between 5bA and 5bP is "the best" indicator of positivity (that is, 5bA is the "best " metabolite when compared to pregnane ERC and it was non-positive in Floyd). He also advanced an argument (and tied it to delta 5bA and 5bP) that LNDD made an error, causing excessibely low 5aA in Floyd, and thus a "positive" when it was compared to pregnane ERC.
On the surface it looks like a good argument but it's one-sided. It ignores OTHERS studies. Catlin conducted studies that clearly indicate that urine metabolites in control individuals are excreted at different rates. This depends on many factors including the ROUT OF ADMINISTRATION (patch, oral) and thus it would NOT be unexpected to find different concentrations following T. administration. It appears that T delivery system has an impact on metabolites. It's my personal speculation that WADA knows it. It's possibly related to the fact that, for example, digestive system may alter orally administered T or T metabolites compared to a patch-delivered T or T metabolites that go straight into circulation.
Again, it's a point that could be argued either way. It particularly makes sense for Floyd's defense if the above mentioned partial contamination could be tied in.[/quote]Cooments by OMJ and my responses on the subject from the same thread.
[quote]OMJ: Are you suggesting that the route of administration can affect isotope ratios? I haven't seen any evidence of that. Yes, metabolites are excreted at different rates, but we're not talking about levels of metabolites here, but isotope ratios.
[quote]RH:I am not sure if it does but I would not exclude it. You have a point. I should have been clearer. I was suggesting that the studies we've examined here so far did not clearly identify the route of administration. Catlin's, Aguilera et al study from 2001 said nothing about the route. The Maitre work (the basis for Jacobs submittal) on the other hand clearly refers to "Oral". I am making an assumption that the route of administration may be a contributing factor to different dominating metabolites as regard their C13 content. For example, what Jacobs called "the best" metabolite (5bA, not elevated in Floyd) was in reality characterized as the most robust for detecting T abuse in terms of LONGER DETECTION PERIOD. So, some kind of poorly understood artificial manipulation (route and something else) may be targeted at stressing 5aA for a shorter period hoping to beat the detection window.[/quote]
[quote]OMJ:Floyd's defense is not claiming that the isotope ratio of 5bA is high, but that the ratio of 5aA is too low. Hence the very large difference values, -5.5 to -6.4, when compared with pregnance.
[quote]RH:I made a typo. I meant to say "a more negative 5aA". True, Floyd's team argues the measurement error is confirmed by published negative controls data. Specifically, they site
Catlin's mean, maximum, minimum were at -26.35, -25.55, -27.89 correspondingly and Maitre's mean of -24.3 whereas Floy's was -28.40 for A- sample and -28.31 for B-sample.
I would agree with you that the measurement error can be easily excluded. But for a different reason. You pointing to other metabolites being OK would hold ONLY
if we are talking about bias or linearity (it's just one of 6-7 criteria). It would not apply if "span error" developed. But overall, I agree, machine error is of low probability. Also, it can be disregarded on the basis of consistency between A and B readings (taken days apart, at different calibrations) and by 3 verifications of each sample (below -28)[/quote]
[quote]OMJ:...we could conclude that 5aA is more sensitive than 5bA, both decreasing faster upon T administration, and returning to baseline faster later.
[quote]RH:That's how I read it too.[/quote]
[quote]OMJ:So are the control values they report true or corrected? If true, this is very damning evidence against Floyd, scientifically, though legally I'm not sure it can be used. It shows that his 5aA values are about 4 delta units lower than control values. If the control values are corrected, however, they are almost identical to Floyd's, actually slightly lower, and this would be strong evidence that Floyd did not dope.[/quote]
[quote]RH:I really don't know. I would think that all the values should be "corrected" if meaningful comparisons across different studies should be made. The clue couldbe found in how
WADA defines -28 limit. They specifically said "based on non-derivatised steroid"[/quote]
[quote]OMJ:The most damning thing I find about Floyd's difference values is that they are all negative, and almost all negative by more than 2 delta units. That probably corresponds to about 2.5 SDs. That is highly significant for even one comparison, for four different comparisons, a meta-analysis would probably show significance off the charts.[/quote]
[quote]RH:I also find this difficult to explain by anything except some kind of contamination that went beyond cleavage and started creating new steroids with unknown C13 ratios.