Diagnosing acute lymphoblastic leukemia (ALL) and its subtype usually involves performing a series of tests. Doctors commonly use blood tests and bone marrow tests.
Your doctor needs to test your blood to make a diagnosis. Your blood is sent to a lab for a complete blood count (CBC), which shows the number of red cells, white cells and platelets in your blood. If you have ALL, you'll have lower-than-normal numbers of red cells and platelets.
Bone Marrow Tests
Your doctor or oncologist (cancer specialist) tests your bone marrow. Bone marrow testing involves two steps usually done at the same time in a doctor's office or a hospital:
- a bone marrow aspiration to remove a liquid marrow sample
- a bone marrow biopsy to remove a small amount of bone filled with marrow
The tests' purpose is to confirm an ALL diagnosis and:
- find out how many ALL cells are in your marrow
- examine the cells to look for certain abnormal changes and characteristics
- identify the ALL subtype by examining chromosomes and genes
- develop a treatment plan
Lab Tests to Confirm a Diagnosis and Identify the ALL Subtype
After your doctor takes samples of your blood and bone marrow, a hematopathologist confirms a diagnosis and identifies the ALL subtype. A hematopathologist is a specialist who studies blood cell diseases by looking at samples of blood and marrow cells and other tissues.
When examining your blood and bone marrow cells, the hematopathologist identifies ALL by:
- specific chemical activity in blast cells
- characteristic markings (antigens) on the blast cells' surface
- the number and size of chromosomes
- the percentage of leukemic blast cells present
The hematopathologist uses one or more lab tests such as those below to examine your cells:
- Cytogenetic analysis identifies certain changes in chromosomes.
- Immunophenotyping looks for antigens on the blast cells to identify the subtype. Flow cytometry is one type of test used for immunophenotyping.
- Genetic testing, such as polymerase chain reaction, analyzes certain genes for changes in their structure or function.
A common marker that doctors look for on the ALL cell surface is called cALLa (common acute lymphocytic leukemia antigen). This marker is also called CD10 (CD stands for cluster designation).
Cytogenetic analysis identifies chromosome or gene abnormalities in the ALL cells, such as:
- more than the normal number of chromosomes
- fewer than the normal number of chromosomes
- other chromosome abnormalities, such as a translocation between chromosomes 12 and 21 or a translocation between chromosome 22 (the Philadelphia chromosome) and chromosome 9
If you're diagnosed with ALL, you may need to undergo more blood and bone marrow tests during or after treatment to see how your ALL cells are responding to therapy.