Researchers are facing calls to retract published findings that link chronic fatigue syndrome to a retrovirus called xenotropic murine leukemia virus related virus (XMRV) after new scientific criticism of their validity.

Editors of the journal, Science, have issued an “editorial expression of concern” over a research paper it published in October 2009, saying the report is “now seriously in question.”

The study, “Detection of an infectious retrovirus, XMRV, in blood cell of patients with chronic fatigue syndrome,” was led by Vincent Lombardi and Judy Mikovits of the Whittemore Peterson Institute, Reno, Nevada (Science 2009;326:585).

It purported to show that a retrovirus XMRV was present in the blood of 67% of patients with chronic fatigue syndrome (CFS) compared with 3.7% of healthy controls.

The study caused a stir when it appeared and led to some CFS patients, believing XMRV to be a possible contributor to their condition, seeking antiretroviral treatments marketed to combat HIV.

But Science, which is the weekly journal of the American Association for the Advancement of Science, has now highlighted “flaws” in the paper.

Since 2009, it says, at least 10 studies conducted by other investigators and published elsewhere have failed to detect XMRV in independent populations of CFS patients.

Furthermore, Science …