Hi, you raise a good point here.
The Oxford Criteria states there need not be any 'specific symptoms' to qualify for a diagnosis of CFS.
Although the Fukuda Criteria are very weak, they do require at least, 4 symptoms.
Now why is this important regarding the recent 'failed' UK XMRV study?
Recently, I read a response from Dr Anthony Cleare on the PLOS One website
in a reply to crticism of the Imperial College Study. Link
And I found this quite remarkable comment that you may be interested in.
''In addition, we also exclude patients with chronic somatisation disorder as defined by DSM-IV, which is not required by the Fukuda criteria
So Dr Cleare is making 'clear' that people with CFS Fukuda criteria diagnosis may not be organically ill when studied for XMRV.
This problem of selecting the wrong people to study, is in stark contrast to the WPI folk, who selected people very much organically ill, which was aided by using
Canadian Criteria CFS that is the most 'strict' out there for CFS. (Hence it was logical the WPI seleced it, if trying to search for a
retroviral cause for overwhelming chronic exhastion).
If Fukuda criteria CFS 'allows' people with no organic disease to be studied for XMRV infection who are suffering from somatization disorder, not CFS (According
to Dr Cleare). Then it's imperetive than studies on XMRV, (or even any other study) not use Fukuda Criteria ever again.
If this is a risk, then when using Oxford '91 criteria that has no symptoms that need to be specific to be told one has CFS, then Oxford '91 criteria
should never be used to 'search' for biological diseases, especially in a cohort of patients who are having blood tests done for a newly discovered retrovirus!
The good news is (after all the damage it's done) the Imperial College Study has been shown to have holes in it too deep
to be a valid study. Yes the media have jumped all over it, but real Scientists understand it's not a 'like for like' study.
After all if I pan for gold in the hills of Detroit in 1850 and claim there is no gold, it's different than panning for gold in the hills of California.
Unfortunately for patients, the general public and even many doctors, don't own a medical atlas with historical fault lines....
and additionally XMRV is never going to be found by researchers (due to selection bias) in patients whose CFS symptoms are described as 'learned helplessness'.
(Butler et al, 1991).