The symptoms of acute lymphocytic leukemia (ALL) are similar to those of other blood diseases. An accurate diagnosis requires a thorough physical examination, a complete medical history and several diagnostic tests. The tests may include the following.
Complete Blood Count (CBC)
This test examines blood for the number of red blood cells, white blood cells and platelets.
Peripheral Blood Smear
A blood sample is examined under the microscope for the number and types of white blood cells and the presence of ALL blasts (leukemia cells).
Immunophenotyping (Flow Cytometry)
A sample of blood cells is examined through a sophisticated machine called a flow cytometer to see if leukemic cells are present and whether they are the B-cell or T-cell type. (Most cases of ALL are of the B-cell type—85 percent).
Bone-Marrow Aspiration and Biopsy
A sample of bone marrow and a small piece of bone are taken from the back of the pelvic bone using a hollow syringe. The cells are then examined under a microscope to see if leukemic cells are present. While this short procedure can cause some brief pain at the biopsy site, it provides valuable information about the bone marrow and blood cells.
Under a microscope, blood or bone-marrow cells are examined for changes in their chromosomes. Some types of leukemia present with an abnormal number of chromosomes. In other forms of leukemia, two chromosomes exchange some of their DNA in what is called a translocation. About 20 to 25 percent of adult ALL patients and up to 50 percent of patients over the age of 60 years have a translocation between chromosomes 9 and 22—the Philadelphia chromosome. (Discovered in Philadelphia in 1960, this was the first chromosome abnormality definitively linked to cancer.) Presence of the Philadelphia chromosome requires special treatment.
Fluorescent in Situ Hybridization (FISH)
The fluorescent dyes used in this test attach to specific parts of certain chromosomes. More chromosomal abnormalities can be seen under a microscope using this technique. It is important because some subtypes of ALL have distinctive translocations that are difficult to detect with simple cytometric analysis.
A small needle is advanced into the spinal cavity in the lower back, and a small amount of cerebral spinal fluid (CSF) is withdrawn. The CSF is then examined for abnormal blood cells to determine whether the cancer has spread to the spinal fluid.
Imaging tests such as chest X-ray, CT scan or ultrasound exam may be performed to determine whether the leukemia has spread to other parts of your body.