An accurate diagnosis of the type of leukemia is important. Diagnosing acute myeloid leukemia (AML) and your AML subtype usually involves a series of tests.
Tests Your Doctor May Use to Diagnose AML
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 AML, you'll have lower-than-normal numbers of red cells and platelets.
- A peripheral blood smear, which shows whether you have too many immature white cells (leukemic blast cells) in your blood and too few mature white cells.
Bone Marrow Tests
Your doctor or oncologist (cancer specialist) tests your bone marrow. Bone marrow testing involves two steps usually performed 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 AML diagnosis and:
- Find out how many AML cells are in your marrow
- Examine the AML cell type and look for certain abnormal changes
- Identify the AML subtype by examining chromosomes and genes
- Develop a treatment plan
After your doctor takes samples of your blood and bone marrow, a hematopathologist confirms a diagnosis and identifies the AML 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 marrow cells, the hematopathologist identifies AML by:
- The percentage of leukemic blast cells present
- Specific chemical activity in blast cells
- Characteristic markings (antigens) on the blast cells' surface, such as CD13 or CD33 (CD stands for "cluster designation")
- Percentage of blast cells
- Cells based on the types of markers (antigens) on the cell surface.
Blast cells normally make up 1 percent to 5 percent of marrow cells. When blasts make up at least 20 percent, a diagnosis of AML can generally be made. However, one AML subtype - M2 AML (myeloblastic with maturation) - can be diagnosed with less than 20 percent blasts based on cell appearance.
The hematopathologist uses one or more of the following lab tests to examine your cells:
- Cytogenetic analysis and karyotyping identifies certain changes in chromosomes and genes.
- Immunophenotyping looks for antigens on the blast cells to identify the subtype. Flow cytometry is the name of one test that may be used to do immunophenotyping.
- Polymerase chain reaction (PCR), a genetic test that analyzes certain genes, such as FLT3 and NPM1, for changes in their structure or function
Chromosome and Gene Abnormalities
About 60 percent of people with AML have abnormal chromosomes (number and/or structure). These may affect a patient’s response to treatment. Certain changes to chromosomes and genes can provide important information for treatment planning.
AML patients with normal chromosomes may have genetic mutations. Your doctor will perform a molecular analysis on your cells to identify genetic changes.
Access the booklet Acute Myeloid Leukemia for a full listing of chromosome and gene abnormalities.
If you're diagnosed with AML, you may need to undergo more blood and bone marrow tests during or after treatment to see how your AML cells are responding to therapy.