That is way my labs were for about 6 years. FISH sometimes at negative, but sometimes would show 1% to 3 % + while PCRU.
I know my new oncologist was confused, too, so he ran a test to see if I had other mutations, because the BCR/ABL lab, only checks for #9 & # 22, I think that would be the P210. I did not have any other mutations only the P210 BRC/ABL, same as when diagnosed.
The FISH (3/19/12) came back at 1.5 % positive, which was 3 nuclei out of 200, but the PCR was 7 %. I have only had 1 lab there. The onc said he would do two more labs before final conclusions. At consultation back in Nov 2011,my new oncologist did say, he did not go by the national guidelines, as treatment is a very individual thing. He said as long as I stayed in a range, even if it was not PCRU, that was Ok, as long as numbers did not steadily go up. He is a CML Specialist at the #1 cancer center of indiana. Although when the nurse called me about the FISH & PCR, for some reason she seemed only concerned about the FISH. She did mention Tasigna, She was not present when I talked to doctor, so I don't know what is up with that. I did mention to her I wouldn't want to think about changing anything, at least not until I turned 65 next January as I would be Medicare age. My Blue Cross give me grief about paying anything, it is an uphill battle. I usually get them to pay but only after several exhausting phone calls and a push of saying OK I am calling the UAW Benifit rep, that seems to make a difference and to think it has been 6 1/2 years and still the same hassle. Anyhow the nurse said no worry you are not in any imminent danger. So I'm cool with that. I know chronic is slow, so as long as I do the labs and we watch the numbers are not steadily going up, I'm good with that. I read where you can still be under radar and have a million or so PH+. In fact I don't think the disease has changed at all for me, I think it is just the lab was reporting and changing over to IS.
My old labs were sent from my home state Indiana to N.J. My new labs are draw in the oncologist office and interpreted at the lab/hospital that is connected to his office. I think part of the confusion has something to do with where/how the labs do their calculations. I don't know.
It does seem odd, but it has been an ongoing thing for 6 1/2 years for me of sometimes the FISH showing a slight positive an PCRU and I don't not have any other mutations.
Seem like circumstance and situations vary from person to person and doctors and labs and TKI's.