FDA: not all XMRV assays have been validated

Testing Strategies for Detection of Xenotropic Murine Leukemia Virus Related Virus (XMRV) Infection

Shixing Tang and Indira K. Hewlett:

Laboratory of Molecular Virology, CBER, Food and Drug Administration, Bethesda, MD 20892
Correspondence should be addressed to Shixing Tang, shixing.tang@fda.hhs.gov; or Indira Hewlett, Indira.hewlett@fda.hhs.gov

Unfortunately, all of these assays have not yet been fully validated due to lack of reference reagents for standardization of assays; therefore it is difficult to make comparisons of results obtained in different laboratories using various methodologies.

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Conclusion:
Currently there are no commercially available, FDA approved/licensed tests for detection of XMRV or other MLV-related human retroviruses. Standards for the diagnosis of XMRV or MLV-related retrovirus infection based on laboratory test methods have not been established. The relative sensitivity and specificity of various assay methodologies and strategies (i.e. NAT, serology, culture) have not been determined and standards for assay performance have not yet been established. The use of multiple testing methodologies may be required because of the biology of the viruses, such as transient viremia and relatively low immune response observed in the Macaque model. In order to avoid false positive detection, mouse DNA contamination should be carefully examined and excluded.