Sometimes science works the way it’s supposed to. Scientists make hypotheses, test them by gathering preliminary evidence, and then argue about the inevitable conflicting results. Eventually better and better evidence is gathered until a consensus is achieved. Actually, I think that is how science usually works, it’s just that most questions in science are narrow and technical and don’t command media or public attention. Those that do tend to be the more enduring controversies or where a particular special interest (ideological, social, corporate, etc,) is involved.
In medicine scientific controversies may take on a life of their own, or become manufactured controversies (manufactroversies) that endure long past any genuine scientific debate. Such false controversies are often driven by patient groups who feel they are not being treated fairly or honestly, or by practitioners who do not want to give up on their favorite (lucrative) modality. This leads to a disconnect between the scientific controversy and the public controversy – a frequent theme on SBM.
I am happy to report that one such controversy has taken a turn for the good – a recent study has provided fairly definitive evidence that chronic fatigue syndrome (CFS) is not associated with either the XMRV or the pMLV viruses. The study was a consensus trial with both sides in the controversy collaborating to address all the criticisms of the earlier conflicting studies.
A mouse leukemia retrovirus, xenotropic murine leukemia virus-related virus (XMRV retrovirus), has been under consideration as a possible cause of chronic fatigue syndrome (CFS, and also prostate cancer). In a study published in Science in October 2009, Lombardi et al. found XMRV in 67% of CFS patients and 3.7% of controls. Several subsequent studies in the UK, the Netherlands, and the US — by lead authors Erlwein, van Kuppleveld, Groom , Switzer and Henrich — failed to find XMRV at all.
Now a new study published in Retrovirology by Hue et al. shows that the original positive findings were likely erroneous and due to contamination in the lab. The complete article is available online.
We provide several independent lines of evidence that XMRV detected by sensitive PCR methods in patient samples is the likely result of PCR contamination with mouse DNA and that the described clones of XMRV arose from the tumour cell line 22Rv1, which was probably infected with XMRV during xenografting in mice. We propose that XMRV might not be a genuine human pathogen.
When I first heard that a retrovirus had been identified as a possible cause of chronic fatigue syndrome, I withheld judgment and awaited further developments. When I heard that two subsequent studies had failed to replicate the findings of the first, I assumed that the first had been a false alarm and would be disregarded. Not so.
It’s a classic case of wishful thinking outweighing good judgment. One unconfirmed report of an association between the XMRV virus and chronic fatigue syndrome (CFS) resulted in a rush to test for the virus, speculation about possible implications, and even suggestions for treatment. And the subsequent negative studies did little or nothing to reverse the trend.
XMRV is Xenotropic murine leukemia virus-related virus. In the past, there were reports that this retrovirus was associated with prostate cancer, but then other reports found no link. In 2009 a study was published in Science, “Detection of an Infectious Retrovirus, XMRV, in Blood Cells of Patients with Chronic Fatigue Syndrome” by Lombardi et al., reporting an association with CFS:
we identified DNA from a human gammaretrovirus, xenotropic murine leukemia virus–related virus (XMRV), in 68 of 101 patients (67%) as compared to 8 of 218 (3.7%) healthy controls. (more…)