If you have symptoms that suggest you may have leukemia, your doctor will first probably want to check your blood to see if it has normal numbers of blood cells. People with leukemia often have abnormally high numbers of white blood cells. The blood may also have immature blood cells, called blasts, which are normally found only in the bone marrow. If leukemia seems likely, your doctor will perform the following test to 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. Your doctor may also do this test after treatment to check its success.
A doctor usually does this test on bones of your hips, although other bones, such as the breastbone, can be used as well. Before making a small cut in the skin, the doctor numbs the area with a local anesthetic, which you usually get as an injection. Then the doctor inserts a needle to remove a small amount of liquid marrow from the bone. You may need to have this done on both hips. Next, the doctor uses a larger needle to remove a solid piece of bone and marrow. Even with anesthesia, you may feel uncomfortable as the doctor removes the marrow and bone.
After he or she has removed the marrow and bone, your doctor sends the removed samples to a lab where a special doctor, called a pathologist, checks them for leukemia cells. Using these samples, pathologists may also perform these tests:
Immunophenotyping. Tests, such as immunohistochemistry and flow cytometry, can be used for immunophenotyping. These tests require a sample of either your blood or your bone marrow. Immunophenotyping measures the types and amounts of antigens on the surface of leukemia cells. Antigens are substances that prompt an immune response. Your doctor uses these facts about your antigens to learn what type of leukemia you have and how the leukemia may grow or spread. Results of this test may take several days.
Cytogenetic analysis. This test requires a sample of either your blood or your bone marrow. The cells are then grown in a laboratory. 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 example, 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 an extra copy of 1 can be added. This information will affect your treatment plan. You will likely get results from this analysis within a few weeks.
Molecular genetic tests. Other tests may be done on blood or bone marrow samples to look for DNA changes. Fluorescent in situ hybridization (FISH) is a very sensitive lab test that uses fluorescent dyes to detect some chromosome changes that can't be seen with standard cytogenetic testing. It also provides results within a few days, which is why many centers now use this test. Polymerase chain reaction is another very sensitive DNA test that can find some chromosome changes too small to be seen with a microscope, even if very few leukemia cells are present in a sample.