Five days after Science withdrew a controversial study linking chronic fatigue syndrome (CFS) to a virus, another research paper on the topic has been retracted.
This study, retracted by the Proceedings of the National Academy of Science on 27 December, was widely seen as supportive of the proposed link between a virus and CFS, so its retraction is another blow to those who back that connection. It had found that people with chronic fatigue syndrome were more likely than healthy controls to harbour MLV-like viruses in their blood. (MLV stands for murine leukaemia virus; and the virus singled out for attention by the Science paper, XMRV, is a member of the MLV-like family of retroviruses).
Publication of the PNAS study had been delayed last year, while it underwent a last-minute additional round of review (see ‘Chronic fatigue findings were held back‘). It was eventually published in August 2010 (see ‘Delayed chronic fatigue syndrome paper to be published‘), but even then the authors acknowledged that they were unable to provide the additional evidence requested by the last panel of reviewers.
In a lengthy retraction letter, the authors note that the findings they reported were reproducible in their own laboratory and that there was no evidence of contamination in their samples. But they listed four reasons for retracting the work, including insufficient patient samples to send to other labs for confirmation of their results, and their own inability to establish the presence of the retroviruses using other methods, such as culturing them or demonstrating the presence of anti-MLV antibodies in patients.
For a summary of the arguments around chronic fatigue syndrome and viruses, see Nature‘s editorial, Cause for concern; while Retraction Watch has more details on the latest PNAS retraction.