Welcome to this forum,
You may find it helpful to read (and re-read) our booklet on CML and testing/monitoring. It take some time to understand this disease as well as how the various tests show your response to therapy. Take a look at our booklet/primer - link is on our home page... see a snip below:
Genetic Tests used at diagnosis and in the first months of TKI therapy:
Some sort of genetic testing will be done to look for the Philadelphia chromosome and/or the BCR-ABL1 gene. The following types of tests can confirm or deny a diagnosis of CML.
Cytogenetics: also called Karyotyping
Chromosomes can only be seen when cells are in the dividing phase. Blood or marrow samples are cultured in the lab so that the cells begin to grow and divide, although this is not always successful. The dividing cells are looked at under a microscope to assess the number of immature vs mature cells as well as changes to chromosomes (pieces of DNA) and, in the case of CML, to detect the Philadelphia chromosome. Sensitivity is limited, typically detecting 1 out of 20 cells tested. Even when the Philadelphia chromosome is not seen, other tests can confirm the presence of the BCR-ABL1 gene.
Qualitative PCR - used at diagnosis to confirm or deny a diagnosis of CML.... i.e the presence of Ph+ cells / Bcr/Abl gene
FISH- tests upwards of 50-200 cells.... a more sensitive test than cytogenetics.
RT qPCR- (Quantitative qPCR)
What this test measures and its relationship to other tests:
After the start of therapy, q-PCR is used at specific time points after cytogenetic/FISH tests. Once tests show that the Ph+ cell population has reduced to less than 10%, the q-PCR test can more accurately quantify the amount of residual disease left in the marrow.
The goal of TKI therapy is to reduce the abnormal BCR-ABL1 gene to a deep molecular level, preferably to at least 0.1% (MMR/MR3)
During the first 3, 6, 9 and 12 months of therapy Ph+ cells should reduce significantly.
When the level of Ph+ cells falls below 1% q-PCR testing is extremely accurate and will be used to monitor the stability of a molecular response. Under ideal conditions, this test can detect 1 Ph+ cell in every 100,000 cells, although more commonly it detects 1 Ph+ cell in every 10,000.
Take a look at page 16 for a visual representation of the number of PH+ cells present at diagnosis vs the reduction you would want to see at you respond to treatment and through the first year/s of TKi therapy.
I hope this is not too complex for you at the moment. Please ask if you are not sure about your test results etc .
Hope you managed to have a relaxing Xmas.
Sandy
