I read your post in the other thread. It seems well thought out and it certainly seems like you have a better understanding of the science then I do, but my question is: would we not see more of these positives if soy protein was the culprit? It is a really common ingredient. For example, I use perpetuem by Hammer Nutrition and that contains soy protein.
I honestly do not know. There are certainly quite a few cases where people are maintaining their innocence yet accepting their suspension, or arguing 'it was the supplements' - when possibly what I am saying could indeed be the explanation - but it is a defence that no-one has used yet because no-one is aware of it. So it could be that it is indeed a more common explanation than we realise, simply that no-one who has had a positive test has thought to look into it.
Regarding the supplement - If you are regularly taking a soy supplement, at a constant amount each day, the levels of C13/C12 would be the same for both the testosterone and the reference steroid as the intake is steady. What is more likely to cause the problem is if you take intermittent high levels of soy, interspersed with food which has high C13/C12 which is maybe more likely with diet than with regular supplement - we vary our meals -
as that is what may cause the spikes/troughs, which would be out of phase time-wise in your urine for the testosterone and the reference steroid. Possibly it is relevant the digestive problems pro cyclists have during lengthy races - I don't know .
It was particularly surprising that Katie had a positive test when she has been vey anti-doping in her public stance. It is ironic that her own anti-doping stance led her to volunteer for extra optional screening tests, and the very test that came out positive seems like it might (I'm not quite sure - I have lost the link to the article) have been in response to a screening test to the voluntary screening programme that she herself specifically asked to join. I believe that she increased her chances of a false [EDIT - POSITIVE] by signing up for that programme - albeit that it depends on the numbers whether it was likely to be a false [EDIT - POSITIVE]. However - the fact that she was in that screening programme likely increased her chances of being tested at a higher frequency, and if she was being tested at a higher frequency than the average, then that changes the denominator in Bayes theorem (see wikipedia page on Bayesian statistics) making the likelihood that she did in fact dope lower than if she were being tested less frequently. (Possibly it is a similar thing with Tom Danielson - if he were being tested more frequently than the average owing to his prior doping confession, then the denominator in Bayes theorem is lower, making it less likely that he did indeed dope). I would suggest that both Tom Danielson and Katie Compton assuming they are innocent get advice from a proper statistician who understands Bayes theorem rather than simply my amateur explanations. The fact is, that if you are getting tested more regularly then 'Probability of false positive' is greater, meaning that 'Probability that the positive is false given a positive' is lower, because Bayes theorem says:
Probability that the positive is false given a positive = Probability of a Positive X Probability that any given Positive is false DIVIDED BY Probability of false positive
This would be why certain health screens (e.g. HIV before the tests got better) clinic often only screens you for HIV if you are at high risk in the first instance - the test is nearly but not quite 100% accurate, and given the low prevalence of HIV in the population, there are more false positives than you would imagine. (Or at least this used to be the case). Also it is why so many women have cervical cancer scares which turn out to be benign - because cervical cancer is tested for in all women yet is in fact a disease with a very low prevalence rate.