A study supported by the US Department of Health and Human Services (HHS) could not validate or confirm previous research findings that suggested the presence of one of several viruses in blood samples of people living with chronic fatigue syndrome. The new study also could not find the viruses in blood samples of healthy donors who were previously known to not have the viruses.

The HHS-supported study examined the validity of testing techniques intended to detect the presence of several viruses, xenotropic murine leukemia virus-related virus (XMRV) or related polytropic murine leukemia viruses (P-MLVs). The new findings suggest earlier results may have resulted from laboratory error, either contamination or false positive test results.

The initial reports of a link between XMRV and chronic fatigue syndrome prompted HHS to investigate how well tests detect XMRV/P-MLVs, and the prevalence and potential transmission of these viruses in the blood supply. If the viruses had been proven to be present in patients with chronic fatigue syndrome or healthy donors, concerns were raised that these viruses could put the blood supply at risk. The new results were published online in Science Express.

In the new study, blood samples were taken from healthy donors and from 14 patients with chronic fatigue syndrome who had previously tested positive for XMRV or P-MLV, and samples from another person who had tested positive for XMRV but who did not have chronic fatigue syndrome. The study also used blood samples from healthy volunteers whose blood tests previously had shown no signs of XMRV/P-MLV.

The samples were blinded with no indication as to their source, and sent to nine laboratories. The study involved laboratories supported by several HHS agencies along with Abbott Laboratories, Abbott Park, Ill; GenProbe Inc, San Diego; and the Whittemore Peterson Institute (WPI), Reno, Nev.

The nine laboratories tested identical sets of the new blood samples for the XMRV/P-MLV nucleic acid, for replication of the virus (whether it reproduced itself in cells), and for antibodies to the viruses. Two labs, which previously had reported the association of XMRV with chronic fatigue syndrome, reported the presence of XMRV for some samples. However, the labs reported similar rates of finding XMRV in samples from patients with chronic fatigue syndrome and from healthy donors who were known to not have XMRV. Additional tests run in the same and other laboratories on the same samples did not find XMRV, strongly suggesting that these persons were negative for XMRV/ P-MLVs. This would be a sign that the few observed positive results represented false positives — that is, the results indicated the condition was present when it actually was not.

Source: National Institutes of Health