Nagging thoughts It's been a few days and I'm having nagging thoughts regarding the new Groom XMRV study: The latest Groom et al. study found a background level of XMRV similar to that of several US studies (4%) in the blood of their 'healthy controls.' Groom et al. did not find that same background level of XMRV in their CFS patients. Why not? I do not see it stated explicitly in the Groom paper but it appears that the CFS blood samples were stored for 1.5-9.0 years where as the 'healthy control' blood was fresh (can anyone verify or dispute this?). The WPI CFS samples were even older in some cases. Groom et al. appears to have left out a step that the WPI deems necessary: If XMRV, when present, is there in such low numbers and improper storage degrades the ability to detect XMRV, would this account for Groom et al. being able to find a background rate in healthy controls similar to the other US studies while finding nearly nothing in the CFS patient's stored blood (in both groups without the advantage of growing the white blood cells)? Could the issue here be - that low copy numbers and potential degradation in the storage process makes the need to grow the white blood cells before looking for XMRV in stored samples more critical than when looking for XMRV in 'fresh' blood?