George and I keep barking up the same trees. :Retro wink:
I think cohort selection is extremely significant in this (and all) studies, and still find this statement puzzling:
"All patients had undergone medical screening to exclude detectable organic illness, including a minimum of physical examination, urinalysis, full blood count, urea and electrolytes, thyroid function tests, liver function tests, 9 a.m. cortisol and ESR."
That is a very unclear statement, even if we were to look at this without knowledge of the criteria controversies in CFS. Excluding "detectable organic illness" sounds like the old Wessely, and not just a poorly-worded sentence. At the very least, it is a mistake, as it should read "to exclude other organic illness considered exclusionary by the Fukuda criteria", etc.. I really want to emphasize that this is BAD scientific paper writing, folks; they're usually much more careful in the methodology section than this, as nothing embarasses (real) scientists more. Very rare to see those kind of mistakes unless they are NOT mistakes, but actually DO describe the real selection criteria they used.
Note that they only list some of the tests they ran (along with not making clear if these alone, or complete differential diagnoses, were necessary for exclusion from the study).
If XMRV is more difficult to detect in less severely ill patients, as the WPI surmised, and the more severely ill ones also had numerous laboratory or physical abnormalities (what about having HHV6 or EBV positive titers, for instance? Or just lymphocytosis?), then it may be that using their protocols and at this stage in the game it is difficult to detect XMRV in all but those with other positive physical findings. So if that group was excluded, then it's understandable that no XMRV positives would be found.
So we really DO need to find out what exclusionary criteria were used for this study (whether we can ever get an honest answer is another question...).
As for the lack of corroboration in European studies.. there have been only two. One was of CFS patients selected by Wessely, a lousy scientist who favors lousy selection criteria. The other focused on prostate XMRV and was not a CFS study of any kind, to my understanding. So, so far I don't see any valid contradiction of the WPI study until I hear more about the criteria, etc. used by this new study.
ETA: I guess it would be more accurate to say that George keeps barking up the same trees I'm swinging from... Gibbons don't bark...