Phoenix Rising - Cort Johnson's Column
...Presenting complex chronic fatigue syndrome (ME/CFS) research in a way we can all understand.
Tuesday, January 12th, 2010:
XMRV Imperial College Replication Attempt
by Cort Johnson
"And if you see some negative papers coming out, dont be discouraged. Its going to happen. There are going to be some negative papers. People really jump to do this. And the method is not that easy and getting the right bits and pieces you need together (is not easy)" - Dr. Nancy Klimas
The Brits Smack XMRV...Or Do They? - The first XMRV Replication attempt has been published and its a doozy. Originating from the Imperial College in the UK (with patients supplied by Simon Wessely), the study found zero (that's zero!) evidence of XMRV in 186 CFS patients. (Here's a link to an article by the BBC and a link to the original paper .)
The study included a lot of patients (186) who appeared to be pretty ill, had high rates of disability, about 50% of which had infectious onset. They all met the standard CFS Criteria (1994 Fukuda) which meant they did not have a major psychiatric condition.
They used a positive sample of XMRV to ensure that they could find the virus but remarkably, they didn't find the virus in any of the samples - a similar finding to an earlier German study that failed to find XMRV in any prostate cancer samples.
In rather strong terms Dr. McClure, the lead retrovirologist in the study suggested that the WPI had moved too quickly stating "When you've got such a stunning result you want to be absolutely clear that you are 1,000 per cent right and there are things in that [previous study] I would not have done. I would have waited. I would have stalled a little,"
These studies underline how complex situation these efforts are. Earlier the CFIDS Association noted that the German study did not adequately replicate the original XMRV prostate cancer study. Now, Dr. Vernon of the CFIDS Association asserts the same is true with this Imperial College study.
CFIDS Association of America (CAA) States Study Not a Valid Attempt
The CFIDS Association of America posted its response within hours. In a CFIDS Link report Dr. Vernon stated that this study "should not be considered a valid attempt to replicate the findings" of the Science Study and she listed a series of methodological questions that could have interfered with the Imperial College Researchers ability to find the virus. They included:
- Collecting the virus in different kinds of collection tubes
- The DNA from the patients was extracted and purified in a different manner
- They used different amounts of DNA to amplify their assay
- They looked at different parts of the genome
- They ran the PCR under different conditions
Based on Dr. Vernon's experience working with PCRs any of these could have affected the results. Dr. Vernon pointed to a larger much more rigorous study that the Department of Health and Human Services is engaged in. (Both Dr. Vernon and Dr. Mikovits are part of a team overseeing that study). Since that study will involve multiple laboratories that will come up with a standardized test first that study will take longer to finish but it will provide more definitive results. She did say that the CFIDS Association is urging that the DHHS study is completed as expeditiously as possible. She urged patients to be prepared for conflicting results'
"The U.S. Department of Health and Human Services Blood XMRV Scientific Research Working Group is conducting a rigorous study to detect XMRV. Multiple laboratories will standardize methods to optimize sensitive detection of XMRV proviral DNA and viral RNA and then, once methods are standardized, these same laboratories will test coded panels of blood samples obtained from healthy blood donors and CFS patients. We look forward to the results of this study and urge that it be completed expeditiously, especially in light of this report from the U.K. In the meantime, be prepared to read about more studies with conflicting findings. Rather than simply accept or dismiss new information, we will help make sense of why discrepant results occur."
The next day the CFIDS Association of America produced a press release that stated in no uncertain terms their concerns about "many elements" of the study including the rush to publication (three days between submission and acceptance), the different processes used in the two studies and the differing patient groups.
Standardized Test for XMRV - Despite the fact that VIPDx in collaboration with the WPI and Cooperative Diagnostic Labs it's clear there is no accepted test for XMRV yet. (VIPDx was taken to task a bit in one article for providing a commercial test at this point.) Dr. Vernon closed the press release again alluding to a need for a 'standardized test' stating that potentially millions of dollars may be wasted on studies that are later deemed to be invalid because they are not using the correct test. Developing a standardized test requires having multiple labs test and retest different procedures until their results match and they agree they have found the correct test. Only when a standardized test that meets the acceptance of the research community is developed will it be impossible to determine the true prevalence of XMRV. In his CFSAC talk Dr. Coffin agreed that the first priority is developing a standardized test.
The WPI weighed in the next day and in very blunt language took the Imperial College study to task calling it 'meaningless'. Besides the different patient cohorts and different blood sampling procedures they cited:
- The use of a water control rather than a blood control
- Different primer sequences and amplification protocol which was not validated by a clinical control
- Fewer rigorous tests of accuracy
The WPI appears to be asserting that the group should have used an positive sample from a patient rather than the standard XMRV sample they used as a control. They also noted that many more tests of verification the WPI used (involving three different labs).
It's clear that one thing we're going to be seeing are studies replicating their results against standardized XMRV samples (eg Imperial College) or against positive samples from the WPI. Theoretically, if both samples contain XMRV they should produce similar results but if the 'XMRV' in them is slightly different it could create problems.
There are differences of opinion regarding how exact a lab needs to be in replicating another labs results. There are several different PCR techniques and variations within each kind of technique. Some researchers assert that any valid technique should yield positive results. Others believe slight differences can make big differences. At this step of the game - with such a new finding - it seems pretty clear that the first priority is exactly duplicating the original study's findings.
Read more at Phoenix Rising