In the Method, Patients section you state:

"All patients had undergone medical screening to exclude detectable organic illness....."

This sentence should surely read as follows:

"All patients had undergone medical screening to exclude any other detectable organic illness....."

With regard the diagnosis of patients, in the Lombardi et al paper, in addition to using both the Fukuda and Canadian definitions they tested their patients for a range of immunological abnormalities and impaired exercise performance known to be present in CFS patients:

"their diagnosis of CFS is based upon prolonged disabling fatigue and the presence of cognitive deficits and reproducible immunological abnormalities. These included but were not limited to perturbations of the 2-5A synthetase/RNase L antiviral pathway, low natural killer cell cytotoxicity (as measured by standard diagnostic assays), and elevated cytokines particularly interleukin-6 and interleukin-8. In addition to these immunological abnormalities, the patients characteristically demonstrated impaired exercise performance with extremely low VO2 max measured on stress testing."

Whereas in this paper, in addition to only using the Fukuda case definition, the only biological testing of patients involved some basic testing "to exclude detectable organic disease" - these tests do not show significant abnormalities in CFS patients so are merely exclusionary:

".... a minimum of physical examination, urinalysis, full blood count, urea and electrolytes, thyroid function tests, liver function tests, 9 a.m. cortisol and ESR."


Can you please explain why your patient cohort weren't tested for these immunological abnormalities and impaired exercise performance to firstly help to ensure their correct diagnosis and treatment and secondly to ensure as much as possible that the patients in both of these studies had the same disease?

So these two papers on XMRV in CFS involved different diagnostic criteria and different biological testing to choose the patient cohorts.