fmk_RoI said:
So rather than the
two part test allegedly used on the Rio samples, this technology, if developed, could could straight to the chase and need only look at the genes?
The two part test is just looking at the gene sequences. The two parts just look at different sequences. I would think only one of the parts has to work for the test to be successful, though if both come up positive that is even better evidence, would provide statistically higher reliability. No doubt WADA is working on setting the criteria for a positive that can hold up under challenge.
As I said before, one needs to identify a marker sequence, something that unequivocally identifies the gene as exogenous, not native. Viral sequence generally works. The viruses used for vectors, to introduce new genes into the genome, are well characterized, as are the sequences within them that can be used to identify them uniquely.
But there are many possible viral vectors, and doping might use one that the test is not designed to detect. This part of the test can only, at best, rule out the presence of certain viral sequences, probably not all of them (I would have to know more about the details of the test to comment further; with that chip technology we were discussing upthread, one could be pretty exhaustive. Still, absence of evidence is not, as the saying goes, evidence, or at least proof, of absence). Also, there are other ways to gene dope that don't require the use of viruses, though I don't know how likely it would be that an athlete would try this. In any case, then testing for introns is like a backup plan. It's the opposite of looking for a viral sequence, in that now you're trying to confirm the absence, rather than the presence, of something.
This part of the test, though, sounds difficult to me. Many if not most natural genes have introns, so the test would have to demonstrate the absence of the intron in a gene of interest. If you know what the gene is, EPO, then you can just isolate that sequence, and determine whether it has intronic sequences. But if you don't know what the gene being used for doping is, this won't work, and you're left with just the viral sequence test. Though even as I write this, it occurs to me that if you locate the viral sequence, you would locate the gene, so I guess if the viral part of the test is successful, you could go on to the intronic sequence. But if you don't detect viral sequence, and don't know what the gene you're looking for is, there is a problem.
The bottom line is that no test for gene doping that I'm aware of is foolproof. One ought to be able to detect gene doping of EPO, and perhaps some other likely substances, that's attempted through the relatively simplest and most available technology, but as usual with doping, one can ratchet up the arms race, and find ways to evade the tests.
This is where the passport can be very helpful. Even if an athlete is successful in boosting his production of EPO or some other performance-enhancing hormone through gene doping, and even if he avoids testing positive, he should trip signals in the passport test. Indeed, the passport test may help testers decide what genes might have been used for doping, which makes it more likely they will be able to detect them.
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