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a follow-up on bleeding for the cause

A couple of days ago, on my post about World Blood Donor day, one of my commenters noted that the NZ Blood Service is apparently going to follow their Canadian & Australian counterparts in banning people from giving blood if they've ever had Chronic Fatigue Syndrome. (At the moment folks who've had CFS are OK to donate once they're fully recovered.) The reason for doing so is a purported link between CFS & a particular retrovirus (XMRV, or xenotropic murine retrovirus). 

But the link between CFS & XMRV is not particularly clear-cut. A study in Nevada found that >60% of CFS sufferers (N=101) also had traces of XMRV in their blood, compared to <4% of healthy controls (N=218). (Sorry, the link is to Science & may not work for all.) This sounded like something that ERV would be interested in & I was fairly sure she'd written something on it earlier, so I checked. I was right: she's got a very interesting commentary on the methods used by the Nevada researchers. But she's aslo cautious about the overall conclusions: fairly obviously XMRV isn't the sole agent involved in CFS (if it' is an agent), given that 33% of CFS patients didn't express it in their blood. It would also be important to know where the samples came from: if the individuals with CFS lived where XMRV infection is common, then this would skew the results & make any relationship appear stronger than it is. And It does look as if at least some other labs haven't been able to replicate these findings.

I can understand the Blood Service wanting to err on the side of caution, given issues with contaminated blood in the past (the Hep C/haemophilia problem, for example). Consequently I have to disagree with Smut on this one - it probably is better to be safe than sorry. A ban can always be reversed if the apparent XMRV-CFS link turns out to be non-existent after all.

On the other hand, I find it concerning that various commenters, including the lead researcher in the Nevada study, have made statements explicityly linking CFS & XMRV - when a causal relationship has yet to be demonstrated. (It could equally well be an opportunistic infection.) A commercial test for XMRV is now available. While this is valuable as a research tool (in measuring the incidence of infection, for example), identifying a particular individual as +ve for the virus can't at present assist in actually treating the patient. However, in at least some cases people with both CFS and an XMRV infection are taking powerful anti-retroviral drugs (commonly used against AIDS) that can themselves have significant side effects, in the hope that ridding themselves of the virus will also cure the CFS. This seems to be drawing a long bow indeed.

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That article you linked to from was remarkably ill-informed. It states that "XMRV [...] is present in high titers in the blood", which is just weird, because no-one (not even the Nevada team with the positive results) were conducting *quantitative* tests.

Then the author describes CFS as "characterized by [...] chronic inflammation", which must be something he's made up to fit the hypothesis of a viral connection, because it's not mentioned in any of the usual definitions.

A ban can always be reversed if the apparent XMRV-CFS link turns out to be non-existent after all.

That would require someone to admit making a mistake. Bureaucracies don't work like that.

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