Sorry. Too much multi-tasking going on. Hopefully a less garbled version:

There are always a number of possibilities when scientists fail to replicate studies. Here are some possibilities in this case:

Patient criteria/population differences - The study notes that the patients studied met the 1994 Fukada definition, but did not note whether patients also met the 2003 Canadian Consensus Protocols which patients in the study done by the Whittemore-Peterson Institute, the Cleveland Clinic, and the National Cancer Institute also met.

Subgrouping: The reason that scientists made the viral connection between XMRV in prostate cancer and patients with this neuroimmune disease (WHO ICD-10 G93.3 - CFS is included under this organic disease listing along with myalgic encephalomyelitis and post viral fatigue syndrome) is because of a similar immune system abnormality. The R Nase L antiviral pathway was the key. Did not see a notation in Erlwein et al regarding whether their samples came from patients having the same immune system abnormality. Although there may be geographic restrictions on the XMRV virus, the RNase L pathway abnormality has been found in CFS patients worldwide.

Other reasons that Erlwein et al may have failed to find XMRV in CFS patients may have included the following differences in protocol (the WPI study results were confirmed by three independent labs) according to Dr. Suzanne Vernon, former CDC virologist and member of the CDC CFS Research Program team:

• The blood was collected from CFS patients in different types of blood collection tubes. (The failure to use white blood cell culture is another possibility)
• The genomic DNA was extracted and purified using different techniques. (The WPI study used a positive blood sample versus water for the molecular plasmid control)
• The amount of genomic DNA included in the amplification assay was different.
• Different primer sequences were used that amplified different regions of the XMRV proviral DNA without a clinical control.
• The conditions of the PCR amplification assay were different – from the numbers of cycles, to the type of polymerase used.

Dr. Vernon made the following observation regarding the Erlwein, et al study: "...To a microbiologist with experience handling samples and studying various infectious agents (as I am), these variances in procedure could make the difference between detecting XMRV or not. It very well could be true that XMRV is not present in the U.K. as Erlwein, et al. suggest in their discussion, but it is also possible that the technique used in the PLoS ONE paper was suboptimal due to the different methods employed, when compared to the original experiments conducted by Lombardi, et al..."

Dr. Robert Silverman, who was not only a key researcher in finding of XMRV in a subset of prostate cancer patients, but also part of the group that published the landmark findings regarding XMRV in CFS patients in the United States has cautioned "...I would be wary of any hastily performed and presented studies. It takes more time than that to do a proper study, as frustrating as this might be..."

Dr. Jerry Holmberg PhD of the United States HHS Office of Public Health and Science, who heads the United States Blood XMRV Scientific Research Working Group, is working to standardize and validate laboratory methods and reagents for XMRV testing. As previously noted this is important since variations in sample collection and laboratory procedures can produce discrepant results.

Dr. Holmberg also emphasizes the need for careful application of scientific methods to ensure that such studies are conducted with exceptionally high rigor and reliability so that the results provide a solid scientific foundation for moving forward.

PS I was startled to see a comment noting that this two month study only received three days of peer review. I hope that is not the case.


Lombardi VC, Ruscetti FW, Gupta JD, Pfost MA, Hagen KS, Peterson DL, Ruscetti SK, Bagni RK, Petrow-Sadowski C, Gold B, Dean M, Silverman RH, Mikovits JA. Detection of an infectious retrovirus, XMRV, in blood cells of patients with chronic fatigue syndrome.Science 8 October 2009. 1179052

Meeus M, Mistiaen W, Lambrecht L, Nijs J. Immunological similarities between cancer and chronic fatigue syndrome: the common link to fatigue? Anticancer Res. 2009 Nov;29(11):4717-26

Nijs J, De Meirleir K. Impairments of the 2-5A synthetase/RNase L pathway in chronic fatigue syndrome In Vivo. 2005 Nov-Dec;19(6):1013-21

Vernon, SD. XMRV Negative Results Emphasize Need for Robust Replication Study. January 6, 2010. www.cfids.org/cfidslink/2...

United States HHS Chronic Fatigue Syndrome Advisory Committee (CFSAC) testimony October 30, 2009.