I have read the primer which is on this site and it is quite useful but nevertheless would like some comments from those of you that might have more expertise/experience than myself.
I was dx more than 14 years ago and have access to my BCR/ABL scores for the whole period which on perusal makes interesting reading from a 105% ratio from the first bone marrow to some more recent undetectables and with loss of MMR on two occasions.I have had a mixture of some private treatments and some on NHS ,always on imatinib BUT always using the same laboratory-Hammersmith;however I have not been treated there as a patient.Up until April 2019 the IS factor quoted for that lab has been 0.299 but from that date the I.S.Factor has changed to 0.405 -a note on my latest BCR/ABL report states "Due to a change in equipment ,this test is awaiting UKAS assessment".So it looks as if due to replacement and updating of equipment some new calibration has taken place but is subject to further review and assessment.
Now if the initial ratio or % is very small or nearly undetectable then multiplying it by an I .S. factor changes it to some extent
Example: BCR/ABL ratio 0.1 x I S Factor 0.299 = Ratio I.S. 0.0299 My observation would be 0.1 is safe territory but when converted to an IS ratio it looks even safer.
In one instance my BCR/ABL was 0.4 indicating a loss of MMR but 0.4 x 0.299= 0.1196; the raw ratio would be a cause for concern but the adjusted one perhaps would not be.My specialist at that time considered moving me on to another tki such as nilotinib but considering the Ratio I.S.was just above 0.1 did not. A subsequent specialist became quite concerned and ordered mutations analysis ( none found) and upon advice taken from Hammersmith put me on high dose imatinib of 600 mg which then eventually led to some undetectables. So is there still some doubt over the accuracy of I.S.Factors?
I am still unsure whether one should still look very carefully at the raw BCR/ABL ratio or very much depend on the the adjusted ratio that takes into account the I.S. Factor.I fully understand the nature of the PCR test being very sensitive and also the need to try to develop a level playing field between labs ;in addition if one switches labs then one needs to have a comparison tool.However if one has been with a single lab for 14 years I would have questions about the need for/value of an IS factor and also reasons to change it -as seems to have happened recently at Hammersmith.
Any comments or advice from those who may have had similar concerns?