Failure to confirm XMRV/MLVs in the blood of patients with chronic fatigue syndrome: a multi-laboratory study.
Simmons, Graham, Glynn, Simone A, Komaroff, Anthony L et al. · Science (New York, N.Y.) · 2011 · DOI
Quick Summary
Some researchers had claimed that a virus called XMRV might be linked to ME/CFS. This study tested blood samples from 15 people previously reported to have this virus and 15 healthy people without it, sending them to 9 different labs for testing. The labs could not consistently find the virus, and when they did find it, the results were similar in both ME/CFS patients and healthy people. This suggests the virus is not reliably present in ME/CFS patients' blood.
Why It Matters
This study was crucial for the ME/CFS field because it provided evidence that controversial claims linking XMRV to ME/CFS could not be independently verified, preventing potentially misleading diagnostic or therapeutic directions and helping redirect research efforts toward more reproducible findings. It demonstrates the importance of multi-laboratory validation in infectious disease research and established that blood donor screening for XMRV was unnecessary.
Observed Findings
Only 2 of 9 laboratories reported evidence of XMRV/MLV detection despite testing samples from subjects previously reported as positive
Replicate sample results showed disagreement between laboratories, indicating inconsistent detection
Reactivity patterns were similar between CFS subjects and negative control samples
No reproducible detection of XMRV/MLV nucleic acid, viral replication, or antibodies across the laboratory network
Inferred Conclusions
Current assays do not reproducibly detect XMRV/MLV in blood samples across multiple laboratories
Blood donor screening for XMRV/MLV is not warranted based on available evidence
The initial reports linking XMRV to ME/CFS could not be independently verified through multi-laboratory testing
Remaining Questions
Why did some laboratories initially report XMRV detection, and were these false positives or technical artifacts?
Could XMRV or MLVs be present in tissues other than blood in ME/CFS patients?
What biological or infectious factors might contribute to ME/CFS if XMRV is not involved?
What This Study Does Not Prove
This study does not prove that viruses play no role in ME/CFS, only that XMRV/MLVs cannot be reliably detected in blood samples using the assays tested. It does not address whether these viruses might be present in other tissues or whether other viruses or pathogens might contribute to ME/CFS. The lack of detection does not explain the biological mechanisms underlying ME/CFS symptoms.