In a study reported online in Science on Sept. 22, 2011, and presented the following day at the IACFS/ME Conference in Ottawa, Canada by the senior investigator, Dr. Graham Simmons, the XMRV Scientific Research Working Group (SRWG) announced that in a 9-lab study, XMRV/MLV was not reproducibly detected in blood samples.

Blood samples from 15 subjects previously reported to be XMRV/MLV-positive and 15 healthy blood donors previously determined to be XMRV/MLV-negative were distributed among 9 labs in a blinded fashion. These labs performed tests to detect viral nucleic acid, antibody, and viral replication.

Seven labs found no evidence of virus in any samples; two labs did detect virus in some samples, but the results were not replicated between the two labs, and similar viral activity was found in both positive samples and controls.

The authors concluded that present assays (laboratory tests) could not reliably detect XMRV/MLV in blood samples, and therefore routine screening of the blood supply was not warranted.

However, during the question period following his presentation at the Conference, Dr. Simmons confirmed the current recommendation that patients with a diagnosis of CFS or ME not give blood.

Published online 22 September 2011 [DOI:10.1126/science.1213841].