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XMRV and the blood supply: more study needed
Saturday 12 March 2011
XMRV and the Blood Supply: More Study Needed
In the ongoing effort to understand XMRV and related retroviruses, a key concern has been assessing whether a risk exists to the nation’s blood supply. In separate reports published online in the journal Transfusion, two task forces working on the issue say there’s still no conclusive answer.
The task forces were set up in the wake of a study published in 2009 in the journal Science that found the retrovirus XMRV in 67% of 101 patients with chronic fatigue syndrome. XMRV was also found in around 4% of the healthy people in the same study, raising the possibility that people who had the virus but were not sick might donate blood. Subsequent studies have led to conflicting results, with some labs not able to find XMRV or related viruses in either CFS patients or healthy controls.
The task forces charged with assessing risk to the blood supply face a particularly difficult challenge. The science is still uncertain, questions have been raised about whether some samples could have been contaminated with mouse DNA, the virus’s origins and life cycle are still being worked out and scientists continue to debate almost every aspect of the retrovirus.
Amid all of this, blood collectors and federal public health officials have to make decisions without a lot of clear information. They don’t want to exclude donors who don’t need to be excluded, and they don’t want to expose recipients to pathogens that might make them sick.
In December, the blood products advisory committee to the FDA recommended that people with a CFS diagnosis be barred from donating blood. The FDA has not yet ruled on this recommendation. The American Red Cross decided last year to bar people with CFS from donating blood.
In a report published online last week, the HHS Blood XMRV Scientific Research Working Group said that its members evaluated both published and unpublished data to gauge whether transfusion was associated with the development of either CFS or prostate cancer. XMRV was originally discovered in 2006 in prostate cancer patients.
The working group concluded that so far there is no convincing evidence that transfusion is associated with either disease. But because the data are sparse, especially for CFS, the report recommended that additional epidemiologic studies looking for any possible association between transfusion and the two diseases be conducted.
Conducting such studies will be difficult, though, says Susan Shurin, acting director of NHLBI, the NIH agency that is organizing and coordinating the task force.
There is still no agreed-upon test that could be used to screen blood donors, and not enough is understood about the family of retroviruses. “There are too many things we haven’t worked out yet,” Shurin tells the Health Blog.
With many viruses, not everyone who is exposed gets sick. Teasing out the subtle immune deficiencies that might make one person more or less susceptible is very difficult to do in an epidemiological study, she adds.
Efforts to try to get a better handle on the prevalence of XMRV and related viruses among blood donors continue to move forward. There are plans to test blood from approximately 300 blood donors and depending on the results, more studies might be needed. Among the possible studies: evaluating donors in a larger, more geographically diverse group and studying blood samples stored in federal repositories to look at XMRV in donors over time.
The second task force — set up by the AABB, whose members collect most of the nation’s blood supply — reached a similar conclusion. In June, AABB advised its members that people with a diagnosis of CFS should not give blood until more is known.
The AABB interorganizational XMRV task force report, which was recently published online, also concluded that more studies are needed.
Harvey Klein, chair of the task force, tells the Health Blog that the group “remains concerned there may be a transmissible agent.” The task force, which also includes two representatives from Canada’s blood services, holds teleconferences every six to eight weeks to review both published and unpublished data.
Klein says the constant monitoring will allow blood collectors to act quickly if they decide it is necessary. In the meantime, Klein says, “We just don’t know yet.”
The above originally appeared here.
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