Guest guest Posted June 8, 2007 Report Share Posted June 8, 2007 Hi Marcos, I don't believe that we have 95%-100% leukemic cells on diagnosis even though that's what our cytogenetic and FISH tests would have us believe. I'll try to find an article that addresses this issue but my guess right now is that it's closer to 50% of the trillions of cells we have that are leukemic. Once again, if we used your logic, then as soon as we reach CCR (meaning the 20 cells on a cytogenetic exam are negative), we could assume that 100% of our cells are perfectly healthy and we know that is far from the case when we expand the sample size to the sensitivity of a PCR test. Tracey > > > > > > I am not trying to compare FISH with PCR, but comparing how much > > ph+ cell > > > are in my body now (what the PCR is supposed to predict), to how > > much I had > > > at dx. > > > > ****************************************** > > > > Hi Marcos, > > > > The problem with your theory is that if you take your cytogenetic and > > FISH tests from diagnosis to assume that 100% of your cells are > > leukemic, you'd obviously be making a mistake. > > > > With 3 trillion cells in your body, you can be sure that you had SOME > > normal cells in there, which is contrary to what the cytogenetics and > > FISH test would have you believe. This is why I say that you can't > > compare them with the PCR test. > > > > Happy diving, > > Tracey > > > > > > > > > > -- > Marcos Perreau Guimaraes > Suppes Brain Lab > Ventura Hall - CSLI > Stanford University > 220 Panama street > Stanford CA 94305-4101 > 650 329 9920 x 305 > 650 630 5015 (cell) > marcospg@... > montereyunderwater@... > www.stanford.edu/~marcospg/ > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 8, 2007 Report Share Posted June 8, 2007 On 6/8/07, Tracey <traceyincanada@...> wrote: > Hi Marcos, > > I don't believe that we have 95%-100% leukemic cells on diagnosis > even though that's what our cytogenetic and FISH tests would have us > believe. I'll try to find an article that addresses this issue but > my guess right now is that it's closer to 50% of the trillions of > cells we have that are leukemic. Hi Tracey, I thought so far the drs assumed the repartition of ph+ cell is approximately homogeneous in the bone marrow in chronic phase. And I have also read that the fraction of ph+ cells in the peripheral blood is a good representation of the fraction in the bone marrow, or they probably wouldn't use PCR from the blood. But even if it's 50% (factor 2) that wouldn't change all that much the computation of the log reduction, where we care only about orders of magnitude (factors 10). When you say trillions of cells I assume you are saying blood stem cells. > > Once again, if we used your logic, then as soon as we reach CCR > (meaning the 20 cells on a cytogenetic exam are negative), we could > assume that 100% of our cells are perfectly healthy and we know that > is far from the case when we expand the sample size to the > sensitivity of a PCR test. I was saying (or trying to say) the opposite : For the story, my first oncologist told me at dx that all my blood stem cells were all ph+, what didn't make sense to me, and below is about what I told her. (I wasn't happy with this dr for a number of other reasons and I changed after a month.) When a test show 100%, let say the cytogenetics, it doesn't even mean 100% of the stem cells in the BMB tube are ph+, just that when they took 20 of them, all 20 were ph+. But you can estimate the fraction of ph+ from it, and associated probabilities (called p-values), or it wouldn't be a very useful test. It's the same for the FISH and the PCR. The theory that deals with interpreting these numbers is called sampling theory (it's part of what I do everyday at work). From the 20/20 you can compute the probability than the fraction of ph+ cells in the bone marrow is above 95% (at least around the place they took the sample, or overall if you assume homogeneity). From the 20/20 of the BMB and the 100/100 of the FISH, the probability that there are less than 95% of ph+ cells in the area they sampled is low. And it gets extremely low for below 90%. No diving today, have to go to the lab for some meeting At least the marine forecast for the week end is getting even better Cheers, Marcos. > > Tracey > > > > > > > > > > I am not trying to compare FISH with PCR, but comparing how much > > > ph+ cell > > > > are in my body now (what the PCR is supposed to predict), to how > > > much I had > > > > at dx. > > > > > > ****************************************** > > > > > > Hi Marcos, > > > > > > The problem with your theory is that if you take your cytogenetic > and > > > FISH tests from diagnosis to assume that 100% of your cells are > > > leukemic, you'd obviously be making a mistake. > > > > > > With 3 trillion cells in your body, you can be sure that you had > SOME > > > normal cells in there, which is contrary to what the cytogenetics > and > > > FISH test would have you believe. This is why I say that you can't > > > compare them with the PCR test. > > > > > > Happy diving, > > > Tracey > > > > > > > > > > > > > Quote Link to comment Share on other sites More sharing options...
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