Bill Switzer MPH, lead investigator of the CDC XMRV study:
“As reported in Retrovirology, this study used and tested samples that were collected in CDC-sponsored studies of CFS, as well a set of healthy blood donors. Continued efforts are underway to learn more about XMRV, including work with other HHS [Health and Human Services] agencies and non-governmental organizations to standardize testing methods across all XMRV studies.”
“When CDC, FDA, and NIH learned that separate studies had been conducted with differing results, a collective decision was made to try and account for these differences.”
“Timely discussion among researchers regarding the specifics of scientific studies is common and can help them more readily account for the direction of further research. Future research will benefit from the knowledge gained from the Retrovirology study and other studies that have attempted to learn more about this novel retrovirus.”
“Many blood collection tubes with a variety of anticoagulants can be used for virus isolation. The archived specimens we used were collected with anticoagulants that are not known to interfere with either PCR testing or virus isolation.”
“All subjects in the study met the 1994 International Research Case Definition for CFS. One aspect of the definition is its ability to distinguish between subjects who may suffer from CFS symptoms, such as tiredness or depression, but do not have CFS. CDC used samples from CFS subjects who fully met the 1994 case definition and healthy controls that were collected from two previous population-based studies in Wichita, Kansas and metropolitan, urban and rural populations in Georgia. In addition, CFS patients from the CDC Health Care Provider-based Registry of Unexplained Fatiguing Illnesses and CFS were included.
“Thus, CDC used population-based and clinic referral samples. This enabled us to examine sudden onset cases and those that develop gradually. The use of both types of samples in this study helped us to more precisely examine whether or not infection, such as through XMRV, might have played a role in the onset of symptoms.”
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