Hell knows why I'm doing this, too much time on my hands, but here goes.
This 40% false positive for GC-C-IRMS test has been quoted only by Twoggle3 (this is seemingly your source for the information on this point). Twoggle3 links to this research paper:
https://www.doping.nl/media/kb/7048/H%C3%BClsemann%20et%20al%202020.pdfYou will note from the paper that the "40% false positive" statistic is derived from a sample of 5. Yes, that's right, 5. Two out of the 5 participants who ate boar offal in the study resulted in a false positive. You will also note that the authors of that study do not use the phrase "40% false positivity rate", and for good reason. Anyone with a scientific background would refuse to say that a test has a 40% false positivity rate based on a study of 5 participants.
Here's something that Twoggle3 doesn't draw attention to - both of the participants who produced the false positive were male. Now, as someone who thinks critically about these things, I would not rule out that false positives could also occur in women, but I also would not run around shouting about a 40% false positivity rate. If we apply Twoggle3's logic, then the false positivity rate among women is actually 0% (yup, zero). That interpretation is as much garbage as Twoggle's original interpretation, but you see how we can twist figures from scientific studies to confirm our priors.
Next, Twoggle links to the WADA technical report in which a pharmacokinetics analysis was added as an option in cases where boar offal was ingested. The relevant section is 3.2.1 of this report:
https://www.wada-ama.org/sites/default/files/resources/files/td2021na_final_eng_1.pdfRojo and Twoggle claim that these new rules state that a pharmacokinetics study "must" be done to establish if the nandrolone is exogenous. Let's look at the actual language used in the WADA document:
"The origin of the urinary 19-NA may not be established by GC/C/IRMS analysis, since the varying diets of migrating wild boars lead to dissimilar δ13C values which may range between -15 ‰ and -25 %. Therefore, if the consumption of edible parts of intact pigs is invoked by an Athlete as the unlikely origin of a 19-NA finding, this may be established based on the pharmacokinetics of 19-NA excretion."
So, WADA states that the GC-C-IRMS analysis *may not* establish if nandrolone was exogenous - it doesn't say that it can't establish this. Similarly, it states that a pharmacokinetics analysis *may* be used, it doesn't say that it *has to* be used. This is important since Rojo is using definitive language that is nowhere in the WADA document.
A second, and probably more important point - the GC-C-IRMS test may not be capable of detecting whether nandrolone was exogenous in the cases where the meat is derived from migrating wild boars. Is it possible that a food truck, that buys it's meat commercially, is going to purchase wild boar from a lone hunter? No. They will buy from meat wholesalers, who will buy from farms. There was no need to conduct a pharmacokinetics analysis because there is literally zero chance that the food truck was serving wild boar. This would be easy to establish by simply asking the food truck where it buys its meat. As a result, the GC-C-IRMS test was perfectly fine in this case.
So, if you're going to push this 40% false positivity figure, you need to find evidence that this rate applies in cases where the meat is from farmed boar offal, not migrating wild boars. You're also going to need to show that this rate would scale up to sample that would be generalisable - as a rule, you can never generalise findings from a sample of 5.