I've had cryoglobulenemia, lost it, gotten it back, and have recently tested clear. It's a funny thing. I did have Hepatitis C, then, 18 months after I was treated and the virus became undetectabale, I had an attack of necrotizing vasculitis, which was pretty bad (2003). The blood tests associated with this illness showed cryoglobulins, which hung around for a couple of years, then disappeared, only to reemerge on tests in 2006. I was concerned, but my doctors just said that they'd keep an eye on it. Six months ago I had another round of tests and the cryos are gone. As you mention, the tests are tricky (the blood haas to be kept at just the right temperature, etc.). Aside from the slight possibility that the tests were mishandled, this yo-yo thing is a mystery. I'm glad I'm clear for now. I have no idea whether this helps you at all!! Good luck.