Chronic fatigue syndrome not linked to suspect viruses

It has been suggested that chronic fatigue syndrome (CFS) – or myalgic encephalomyelitis (ME) - is not caused by the virus xenotropic murine leukemia virus (MLV) – related virus (XMRV), nor by polytropic MLV (pMLV).

The findings were discovered in a study commissioned by the National Institute of Allergy and Infectious Diseases.

The study subjects were chosen following laboratory screening and extensive clinical assessments from six sites across the US. In total there were 293 subjects – 147 with CFS/ME and 146 matched controls.

All CFS/ME patients were aged between 18 to 70, had never suffered from another neurological or psychiatric illness, met both the "Fukuda" and "Canadian Consensus" criteria, had symptoms of a viral infection before the onset of CFS, had reduced scores on the RAND36 quality-of-life survey and weren't pregnant, lactating or less than three months post-partum.

Control subjects were enlisted to match age, gender distribution, race and geographic location, with no prior contact with CFS patients.

All subjects were then examined for confirmation of any disease that may cause fatigue, including metabolic, endocrine, or infectious.

Molecular, culture and serological methods were then used on blood collected from the patients and analysed under blinded conditions for XMRV and pMLV.

None of the laboratories found proof of pMLV or XMRV in samples from the recruited control or CFS subjects.

The diagnostic procedures that were utilised were confirmed as operating accurately and quality assurance of the molecular tests was verified through using separate positive and negative controls.

XMRV/pMLV-reactive antibodies were positive in nine control and nine CFS blood samples.

As there are no positive controls in the general population with XMRV serology, the accuracy of this assay cannot be determined, the researchers concluded.

Nevertheless, there was no correlation of antibody reactivity in blood from CFS and control samples.

"Although I am disappointed that we found no association of XMRV/pMLV to CFS, the silver lining is that our 2009 Science report resulted in global awareness of this crippling disease and has sparked new interest in CFS research," said Dr Mikovits, the author of the Science paper wherein XMRV was first linked to CFS.

Posted by Ben Evans