Confirming Your Diagnosis of CML
The following 3 tests can help confirm the type of leukemia you have and what your prognosis is. A prognosis is a statement about the prospect of surviving and recovering from a disease.
This test requires a sample of either your blood or your bone marrow. The cells are then grown in a laboratory. After several days, a pathologist uses a microscope to see the cell's chromosomes, which are pieces of DNA that control cell growth. The DNA changes related to leukemia are not inherited, but occur after birth when the cells become leukemia cells. With some types of leukemia, chromosomes may exchange DNA. For instance, part of chromosome 1 is on part of chromosome 2 and vice versa. This is called translocation. Or there may be the wrong number of total chromosomes. A chromosome can be deleted. Or 1 can be added. Almost all people with CML have the Philadelphia chromosome in their leukemia cells. This means parts of chromosomes 9 and 22 have switched places. This information will affect your treatment plan.
Fluorescent in situ hybridization
Fluorescent in situ hybridization (FISH) also looks for changes in chromosomes. This test uses special fluorescent dyes that only attach to specific parts of chromosomes, such as the BCR-ABL gene in CML cells. It can be used on regular blood or bone marrow samples without culturing the cells first, which means results are available quicker. FISH is also very accurate, which is why it is used in many medical centers.
Polymerase chain reaction (PCR)
For this test, your doctor needs a small sample of your blood or bone marrow. This very sensitive test helps doctors spot the BCR-ABL gene in CML cells, even when they can't find the Philadelphia chromosome. Your doctor may also use this test after treatment to help measure the change in number of CML cells.