Diagnosis
If your child has symptoms of leukemia, see a doctor as soon as possible, as childhood leukemia often progresses rapidly. The doctor will perform a physical exam and take a medical history to try to identify the cause of the symptoms. If the doctor suspects leukemia, he or she will take samples of your child's blood, bone marrow and spinal fluid and have them analyzed for signs of the disease. The doctor may recommend any of the following procedures as part of this process. The child will be sedated for these procedures as they can be painful.
Bone Marrow Aspiration & Biopsy
The doctor performs this procedure to get a sample of the patient's bone marrow for further testing. For this test, a doctor or nurse will numb the patient's hip bone and use a needle to extract a small fragment of solid bone marrow and some liquid bone marrow. This can be done anterior (near the belly) or posterior (back). This test can be done in the hospital or doctor’s office, and some patients can go home right after the test. The doctor will then use a microscope to examine the bone marrow tissue and determine if there are leukemia cells, and if so, how many.
Lumbar Puncture (Spinal Tap)
In this procedure, the doctor uses a thin needle to remove cerebral fluid (CSF) from the lower spine. The skin and tissues over the lower spine will be numbed. The doctor then has this CSF examined for leukemia cells. Chemotherapy, to guard the central nervous system from invasion of leukemia cells, may be injected into the spinal fluid to treat any leukemia cells found there.
The following diagnostic tests may be performed on the blood or bone marrow:
Complete Blood Count (CBC)
A complete blood count (CBC) measures the levels of different types of cells in the blood. Children with leukemia may have elevated levels of abnormal blast cells in their blood. These abnormal cells may crowd out healthy blood cells and cause conditions like anemia, leukopenia, and thrombocytopenia. CBC is a good indirect representation of the marrow function.
Peripheral Blood Smear
In this test, a blood specialist will examine a sample of your child's blood under a microscope. The doctor will look at the appearance and amount of the different types of cells in your blood and look for any abnormalities that may indicate leukemia.
Cytochemistry/Immunocytochemistry
In these tests, the doctor will treat a sample of the blood or bone marrow with special stains or antibodies. These substances react with certain types of cells present in leukemia and produce visible stains that can be seen under a microscope. For example, there is one stain that causes granules in leukemic cells to appear as black spots, allowing doctors to distinguish between acute myeloid and lymphoblastic (lymphoid) leukemia.
Flow Cytometry
Doctors commonly use this test to help diagnose leukemia. In this procedure, the doctor exposes a sample of the blood or bone marrow to special antibodies that attach themselves only to certain substances in the cancer cells. The doctor then passes the entire sample in front of a laser beam, which makes the substances with antibodies attached to them give off light. This test helps the doctor identify the specific types of leukemia cells to get a better idea of the maturity and origin of the cells.
Cytogenetic Tests
The doctor examines the cancer cells for chromosome changes to determine the specific characteristics and subtype of the disease. For these tests, the doctor will grow a sample of bone marrow cells in the laboratory and examine the chromosomes under a microscope once the cells start dividing. Cell division is the best time to examine the chromosomes.
Fluorescent in situ hybridization (FISH)
Doctors also use this test to detect changes in the chromosomes and DNA of the blood or bone marrow samples. The doctor exposes the sample to special dyes that will bind to specific parts of certain chromosomes. These dyes help the doctor detect any abnormalities in the chromosomes known to play a role in leukemia. This test is much faster than cytogenetic tests because the cell sample doesn't have to be grown in a lab.
Polymerase Chain Reaction (PCR)
The doctor may perform this DNA test on a sample of the blood or bone marrow. Doctors use this test to detect chromosome abnormalities that cannot be seen under a microscope because they are too small. This test is very sensitive and can detect these abnormalities even if there are very few leukemia cells in the sample.
Imaging Tests
The following imaging tests are not used to diagnose leukemia. However, the doctor may order these tests to get more information about the progress of the disease or to look for any complications of the disease.
Chest X-Ray
X-rays use electromagnetic radiation to produce images of the inside of the body. The doctor may order a chest X-ray to look for an enlarged thymus or enlarged lymph nodes in the chest.
CT Scan
For a CT scan, the patient lies flat on a table while a machine rotates around the body and takes pictures. A special dye may be injected into the patient's veins and she or he may be asked to drink a special fluid to make the internal organs stand out. The doctor may order a CT scan to look for enlarged lymph nodes in the chest or to check organs that may be affected by leukemia, such as the spleen. Most of the time, however, a CT scan is not needed.
