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XMRV, CFS, and a fuller picture of their dubious connections
Wednesday 23 March 2011
XMRV, Chronic Fatigue Syndrome, and a fuller picture of their dubious connections
Today's story [in the Chicago Tribune] about XMRV, Chronic Fatigue Syndrome, and how they likely aren't linked in the way many CFS sufferers had hoped, offers a cautionary tale about putting too much stake in a single scientific paper.
Every week, many medical studies are published online, making them more accessible than ever to patients.
Many patients are taking advantage of this, reading up on their disease and keeping up on studies as they come out.
But how to make sense of this new research, when it rains down on us almost daily?
Our story today is about the danger of putting too much stock in one study and forgetting that scientific knowledge is hard won, proven over time, and borne out through many, many studies -- not just one.
In this case, a research team peopled with respected scientists looked at blood taken from people diagnosed with chronic fatigue syndrome and healthy people and found evidence of a retrovirus - XMRV - in the blood of both groups. The researchers found evidence of XMRV in the blood of more of the CFS patients than the healthy controls, and they posited that XMRV is linked to CFS.
Their work was published in one of the most prestigious scientific journals in the world, Science, in 2009. It was met with great fanfare and joy from the CFS community, in particular. This is a group that has long felt utterly abandoned by the medical establishment. Nobody knows what causes CFS, and there are no proven cures.
Even treatments are elusive.
Rush to spread "happy" news
Some news outlets - not this one - touted the study as a breakthrough, before further studies could determine if the paper was correct or if XMRV was linked to CFS for sure. Some stories even reported XMRV as the cause of CFS - moving far beyond the paper's conclusions.
The paper's lead researcher, Judy Mikovits, spoke to a CFS patient group. A lab began selling commercial tests for XMRV to patients. Some patients began taking antiretroviral drugs. Some patients put enormous hope in XMRV as the cause of CFS.
If it seems too good to be true...
Scientists know that papers often turn out to be wrong. Even ones that appear in Science. Even ones that have enormously respected researchers at the helm. Even ones that look impeccable.
(Trine did a Trib Nation livechat on XMRV and CFS in December, 2010. It's instructive to look at the full conversation.)
Science, they know, does not move ahead based on a single study. It moves ahead slowly as a body of work that, in time, seems to point in one direction. Questions are asked, questions are answered, slowly a consensus is formed and one idea takes hold. Over time, if that hypothesis is proven wrong by further research, the consensus changes.
And that is what has happened with XMRV and CFS.
Further tests came up empty
After the original paper appeared, scientists all over the world started looking in the blood of chronic fatigue syndrome patients and others for XMRV.
They came up, over and over again, empty-handed. No XMRV, again and again.
But that wasn't enough to close the door. Maybe, they posited, their methods weren't sensitive enough. They changed techniques, looked in different populations of people. Still nothing, test after test.
Others wondered how the Science team got its results, if others could not. A flurry of papers showing how contamination in the lab could explain the results appeared.
And so, almost 18 months later, many studies later, many dollars later, a consensus is forming that XMRV is actually a lab contaminant and not a human pathogen infecting millions.
A cautionary, if not comforting, tale
For patients of all sorts, it is worth keeping this story in mind during Google or PubMed searches of medical studies. A single study, in some ways, means nothing without considering the studies that came before and those that come after. The important question is not, "what did this study say?," but "what do the studies say when considered together? Is there a consensus? If so, what is it?"
Watching the XMRV story is a chance to watch this all in action. A chance to watch science, however slowly, work its way toward the truth.
The above, with comments, originally appeared here.
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