The inability of the second UK XMRV study – this time from a ‘friendly’ research group headed by Dr. Groom – to find any XMRV in a very large sample of patients was rough news for sure. The ME Action Group in the UK took a rather resigned tone in their response while Dr. Vernon highlighted a few methodological issues but mainly concentrated on questions about that original cohort. Neither presented much good news for CFS patients as a cohort answer to the current problems would mean the virus is only present in a very select subset of patients.
In their response to the latest paper the WPI defined the pitfalls they believe researchers face in validating their work – thus basically giving them a guide on how to find XMRV – and doing everybody a big favor.
No Replications Studies Yet Done: They noted that no one has yet attempted to replicate, i.e. exactly duplicate, their original study. In the best of worlds, of course, a true replication study isn’t necessary and is, in fact, irrelevant. How one found the virus, after all, is not particularly important; pathogens can be uncovered by several techniques and researchers typically use different techniques to validate the presence of a pathogen. In fact, a positive validation study using a different technique is considerably more valuable than a replication study because it definitively demonstrates the pathogen is there. It’s only when the validation studies are unable to validate a finding that the issue of a true replication study becomes important – as it now has.
Looking Back – This replication/validation issue was prominent in Dr. DeFreitas retrovirus of almost 20 years ago. The CDC and Gow teams were well versed in retrovirology and had used standard procedures again and again to find viruses. Given their track record they felt little need to change their procedures. (Ultimately the CDC did at least to some degree). But Dr. DeFreitas felt her bug was different. Given her inability to replicate her results she may have been wrong; the question now is whether XMRV is different as well.
Both UK studies used standard XMRV samples to ensure they could find the virus – and their results indicated that they could – but they couldn’t find it in the CFS patients. It may be important, though, that outside of one Japanese study these are the first attempts to find XMRV in the blood and researchers are treading new ground here.
We know that two US prostate cancer studies found XMRV but two German ones did not. We know the German prostate cancer researcher is redoing his study using a different technique. It’s clear that, irrespective of CFS, the field of XMRV research (as small as it is), is quite muddled at this point – perhaps we shouldn’t be so surprised about the bumps in the road encountered thus far.
The WPI took the UK study to task somewhat for not using their reagents, blood, etc. stating that there is only one way to look for XMRV in the blood that’s been validated and that’s their approach and they have a point. The WPI was the first group to ever look for XMRV in the blood and they validated their results as best they could using the Cleveland Clinic and NCI labs. To be fair the Groom study researchers, some of whom have long track records in CFS research, didn’t have any reason to think their procedures wouldn’t work since apparently they do work for most viruses. It’s possible that both they and the Imperial College researchers underestimated the difficulty of finding this virus in the blood.
To their credit they were careful not to overstate their case simply stating in the paper they were unable to find XMRV DNA in their samples and not making broad conclusions about XMRV and CFS. Once the paper came out they’ve stayed out of the spotlight – – they appear to be waiting to see what other studies turn up.
The WPI’s Issues
Most of the issues pointed out by the WPI don’t appear by themselves to be able to account for the differing results in the UK. String them together, though, and you get an interesting scenario.
- Blood Harvesting and Storage – The idea that different blood storage and harvesting procedures could’ve altered the results seems possible but seems unlikely (to this laymen) given that the Groom study used three cohorts from three locations -each of which could have used different storage techniques. We know that XMRV is robust enough for Dr. Peterson to be able to pull XMRV out of a 20 year frozen sample but the possibility does remain that the Groom study inadvertently used blood storage techniques suitable for other viruses but not for XMRV. Laymen’s Conclusion – possibly a significant factor but not likely.
- Different Patients – The idea that the WPI had one set of patients and everyone else had a very different group has come up again and again. The very large size of the British study with patients from several different groups appears to make this scenario an unlikely one (and a decidedly unattractive one since then XMRV would apply only to very special patient groups.) On the other hand some differences in patient selection could start to lower the prevalence rate. Laymen’s conclusion – not ‘It’- but a possibly a contributing factor.
- Different Geographical Prevalence – that XMRV is simply not found in the UK (but is found in the US and Japan) seems have little plausibility given the fact both Dr. Mikovits and VIP Dx labs have stated they’ve found XMRV in samples from UK patients but it’s certainly possible that XMRV could be less prevalent there thus driving down the prevalence a bit (more?). Laymen’s conclusion – not It either but prevalence rates could be lower – we just don’t know.
- Very , Very Low Levels of a Very Difficult to Detect Virus – While the other issues could reduce an investigators ability to find the virus with the exception of the blood storage issue it’s hard to believe they could result in being unable to find any XMRV in a large group of patients. This low viral level issue seems to be more significant, however.
The WPI did two things the other groups didn’t do to find the virus.
- They Usually Grew the Virus in White Blood Cells First in Order to Increase its Numbers. (This presumably involves hitting the white blood cells with a substance designed to enhance viral replication). Dr. Mikovits reported earlier that while XMRV appears to be able to readily infect immune cells it simply doesn’t have the tools to replicate readily in them – hence its viral loads are expected to be low. Three sections of the Science paper detail the cultures the WPI used – a clear indication that the viral levels were very low yet the Groom study used uncultured cells. From a laymen’s perspective this is inexplicable. (Did they think the increased sensitivity of their testing made up for that?) One wonders, as they waded through hundreds of negative results if they ever decided to try to culture the cells first! Note, though that the WPI said they usually, but not always, had to use this technique.
- WPI researchers Had to Search Multiple Times Both in Time and Space to Find the Virus – Not only did they look at a sample multiple times sometimes they had to look at samples taken at different times from the same patient in order to find the virus. The UK studies, on the other hand, presumably looked at the same samples once or twice. (The Retrovirology study looked at their samples twice, once using a more sensitive technique).
Does perhaps a bit different cohort, perhaps reduced rates of XMRV infection in the UK, maybe some blood storage issues and a much more difficult to find than expected virus equal zero findings in two 
UK studies? With true replication studies purportedly on the horizon we’ll know in the not too distant future.
A Confident Group – The WPI asserted, as well, that the best test of XMRV infection, given the difficulty finding it using PCR, is an antibodies test. The Retrovirology group did use an antibodies test but the WPI asserted that it was flawed and theirs is superior.
At the end they stated the only reliable to find XMRV in CFS is to use their approach and basically that no-one’s going to find it until they start using their techniques.