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New Study Finds No XMRV Link to Chronic Fatigue Syndrome, but Debate Continues

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January 17, 2012

UPDATE: In December, 2011, the Editor-in-Chief of Science issued a full retraction of the paper first published online in the October 2009 issue of the journal by researchers at the Whittemore Peterson Institute for Neuro-Immune Disease, who reported finding evidence of xenotropic-murine leukemia virus-related virus (XMRV) in blood samples of patients with chronic fatigue syndrome (CFS). A retraction means that the journal believes that the original article results were due to faulty or incorrect experiments and do not indicate facts. Numerous studies since have not been able to replicate these findings or reliably detect the virus in the previously positive samples. Authors of the report, however, refused to sign the retraction. A second paper, published in 2010, was retracted days after the Science paper from the Proceedings of the National Academy of Sciences, signed by the authors. The 2010 paper had been the only one to support a link between CFS and MLV-related viruses. Although many in the scientific community feel that this issue has been put to rest, one of the lead authors of the original study, Dr. Judy Mikovits, continues to support their claim of a role of XMRV or related viruses in CFS and is awaiting results from a study still in progress,  funded by the National Institutes of Health.

Original article published November 4, 2011:

Current tests do not reproducibly detect Murine leukemia viruses (MLV), including xenotropic-MLV-related virus (XMRV/MLV), in blood samples from people with chronic fatigue syndrome (CFS), so blood donor screening is unwarranted, a recent study concludes.

In the online version of Science published September 22, researchers from Whittemore Peterson Institute (WPI), Cleveland Clinic, and National Cancer Institute-Frederick write that their results may not resolve a dispute that dates back to October 2009, when the same journal published a report suggesting a link between XMRV/MLV and CFS, which has no proven cause or cure. The condition involves overwhelming fatigue that persists with bed rest and can worsen with physical or mental activity.

Authors of the 2009 report found XMRV DNA in 67% of 101 CFS patients and in less than 4% of healthy controls, they wrote, but they didn't make clear the exact nature of the relationship between the viruses and CFS.

AABB (formerly the American Association of Blood Banks) urged blood centers to discourage CFS patients from blood donation, despite no known cases of XMRV contracted through transfusion. (See the news item "XMRV Focus of Change in Blood Donor Policies") Meanwhile, more than a dozen labs in the U.S. and Europe failed to replicate the study's results, and some suggested sample contamination marred them.

The current study was conducted under the auspices of the Blood XMRV Scientific Research Working Group, formed by the Department of Health and Human Services to answer questions about XMRV and blood transfusion. Researchers led by Michael P. Busch, MD, PhD, of the University of California San Francisco, sent blood samples from 15 CFS patients and 15 healthy controls to 9 laboratories for blinded testing with highly sensitive and previously validated methods. Two laboratories reported evidence of XMRV/MLV. However, upon retesting, the virus wasn't found.

These most recent results—which strongly suggest false positive results because of the test's lack of specificity or presence of the virus as a contaminant—may not end the debate. Researchers write they don't exclude the possibilities that the levels of XMRV/MLV markers in blood may be at or below the limit of detection of all tests, or may have dropped lower in CFS patients since the previous studies.

Appearing in the same issue of Science is a partial retraction of the 2009 study, based on Cleveland Clinic researchers' reexamination of the samples they used. It reveals that some were contaminated with XMRV DNA, the retraction says. WPI led the 2009 study and participated in the most recent one and stands by its 2009 findings.

Despite the recent findings, AABB has not changed its policy. In a September 22 statement, AABB said blood centers should still discourage people with CFS from donating, but that its stance is now based on concerns about the health of the potential donor. The American Red Cross precludes those with a medical history of CFS from donating and is unlikely to change that policy until the origins of the condition are better understood.

More research on XMRV and CFS continues to be performed in hopes of resolving this issue. Findings from a study led by the American Red Cross were presented at AABB's annual meeting this month; the researchers found no evidence of XMRV or related retroviruses in tested blood samples from over 17,000 donors and recipients. In addition, other studies are underway. Researchers led by W. Ian Lipkin, M.D., of Columbia University have processed and blinded samples from 150 CFS patients and 150 healthy controls and sent them to laboratories at the Food and Drug Administration, the Centers for Disease Control and Prevention, and WPI. The study's protocol calls for more than one lab testing each sample and, in the case of disagreement, repeated, blinded testing. Results are expected later this year.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used. To access online sources, copy and paste the URL into your browser.

Simmons et al for the Blood XMRV Scientific Research Working Group. Failure to Confirm XMRV/MLVs in the Blood of Patients with Chronic Fatigue Syndrome: A Multi-Laboratory Study. Science Express. Available online at through Published 22 September 2011. Accessed October 18, 2011.

Lombardi et al. Detection of an Infectious Retrovirus, XMRV, in Blood Cells of Patients with Chronic Fatigue Syndrome. Science. Available online at through Published online October 8, 2009. Accessed October 18, 2011.

Partial Retraction. Science. Available online at through Published online September 22, 2011. Accessed October 18, 2011.

National Institute of Health. Press release: XMRV and related viruses not confirmed in blood of healthy donors or chronic fatigue syndrome patients. Available online at through Issued September 22, 2011. Accessed October 18, 2011.

American Association of Blood Banks. Press statement: AABB Statement on XMRV. Available online at through Issued September 22, 2011. Accessed October 18, 2011.

Townsend, Angela. Cleveland Clinic Researchers Retract Findings that Link XMRV to Chronic Fatigue Syndrome. The Plain Dealer. Available online at through Published September 22, 2011. Accessed October 18, 2011.

Gever, John. Medical News: More Chinks in the XMRV-Chronic Fatigue Link. MedPage Today. Available online at through Published September 23, 2011. Accessed October 18, 2011.

U.S. Centers for Disease Control and Prevention. Chronic Fatigue Syndrome. Available online at through Page last updated October 15, 2010. Accessed October 18, 2011.

Cohen, John and Enserink, Martin. False Positive. Science. Available online at through Published September 23, 2011. Accessed October 18, 2011.

Marcus, Amy D. Scientists Say XMRV Poses No Risk to Blood Supply. Wall Street Journal. October 24, 2011. Available online at through Accessed October 2011. 

UPDATED: In a Rare Move, Science Without Authors' Consent Retracts Paper That Tied Mouse Virus to Chronic Fatigue Syndrome. By Jon Cohen. Posted 22 December 2011. Available online at through Accessed January 2012.

Authors Pull the Plug on Second Paper Supporting Viral Link to Chronic Fatigue Syndrome. By Martin Enserink. Posted 28 December 2011. Available online at through Accessed January 2012.