THURSDAY, Sept. 22, 2011 (HealthDay News) -- Researchers have shot another arrow through the credibility of claims that a virus likely causes chronic fatigue syndrome (CFS).
This time, results from nine different labs around the United States failed to differentiate patients with CFS from healthy controls solely on the basis of whether they tested positive for xenotropic murine leukemia virus-related virus (XMRV).
The study was published in the Sept. 22 online issue of Science, along with a partial retraction from the authors of the 2009 study that first fingered XMRV as a probable culprit behind CFS.
This is the 17th study to repudiate the 2009 findings, which were also published in Science, according to a statement released by the Chronic Fatigue and Immune Dysfunction Syndrome (CFIDS) Association of America.
"We share the deep disappointment of many CFS patients and scientists that the initial data did not hold up. Whether you have been diagnosed recently or have been ill for decades, this news comes as a blow to hope for rapid advances in the care available to CFS patients," Kim McCleary, president and CEO of the CFIDS Association, said in the statement.
The 2009 findings raised hopes that there might finally be a concrete cause for this mysterious malady and perhaps, down the line, treatments for the disease. CFS strikes an estimated 1 percent of the world's population, and involves crippling fatigue as well as aching joints, headaches and various other symptoms.
But that hope has steadily been eroded as study after study failed to confirm the initial findings. One study published earlier this year dealt a devastating blow to the theory when it found that the XMRV pathogen spotted in human samples in the first study actually got there as a result of contamination.
At that time, the editors of Science issued an unusual "expression of concern." While they did not call for an outright retraction of the original paper, the editors pointedly questioned the study's validity.
XMRV is transmitted through bodily fluids such as semen, blood and breast milk, according to the Whittemore Peterson Institute for Neuro-Immune Disease.
In the new study, researchers took fresh blood samples from 15 people who had previously tested positive for XMRV or a related virus (14 of them had CFS), and 15 people without CFS who had previously tested negative for the virus.
Nine different laboratories, including two that were involved in the 2009 report, then tested the samples in a blinded fashion, meaning they didn't know which specimens were which.
The only labs to detect XMRV were the two from the original study and, even then, they found the virus just as often in people with CFS as in healthy controls.
One lesson to be learned from this, said study senior author Dr. Michael Busch, is that "we really do need to create blinded panels and validate the performance of tests before they get employed in larger studies so people aren't misled from early data from assays that aren't accurate."
The partial retraction from two authors of the 2009 paper conceded that some of the original blood samples were contaminated, but they stood by the rest of their research.
Although this latest report leaves the quest to find the cause or causes of CFS back where it was in 2009, the upside is that even the negative findings have stirred interest in the disease.
"I think the renewed interest and focus on CFS is good," said Busch, who is director of the Blood Systems Research Institute and a professor of laboratory medicine at the University of California, San Francisco. "There is a lot of research that is going on."
The U.S. National Institutes of Health is sponsoring additional research on XMRV and chronic fatigue syndrome.
"The story doesn't end here. There are many important initiatives underway that give patients every reason to hope for accelerated progress," CFIDS scientific director Suzanne Vernon said in the statement from the association.
The U.S. Centers for Disease Control and Prevention has more on chronic fatigue syndrome.