The Tests That Help Diagnose Leukemia
An accurate diagnosis helps find the most effective treatment options.
Getting an accurate cancer diagnosis is crucial for finding the most effective treatment. Doctors want to find out where the cancer originated, how rapidly it’s progressing, whether it’s spreading, and more—all of which could affect treatment and prognosis.
For leukemia, a cancer that starts in the young blood cells in the bone marrow, many patients’ journeys begin during a routine blood test that shows abnormalities. This could be leukemia, or it could be a number of other conditions (cancerous and noncancerous).
If this is the case, doctors must confirm the diagnosis with other tests for leukemia.
Complete Blood Count
A complete blood count (CBC) measures the number of each type of white blood cells, red blood cells, and platelets, as well as your hemoglobin and hematocrit levels, according to the Leukemia and Lymphoma Society. This checks for abnormalities, which could indicate leukemia (or other types of blood cancer).
“The key components of a CBC are your white blood cells, hemoglobin, and platelets,” says Sangmin Lee, MD, hematologist-oncologist at Weill Cornell Medicine and NewYork-Presbyterian.
For example, your CBC might reveal abnormally high levels of white blood cells (which are actually leukemia cells that don’t function like normal white blood cells).
Bone Marrow Biopsy
Bone marrow tests help doctors assess the health of your marrow tissue and fluid to check for diseases like leukemia. Since leukemia starts in the bone marrow, the cancer cells may appear in the bone marrow before the bloodstream, allowing doctors to catch leukemia earlier.
“Basically, a needle goes into your bone marrow, and a small sample of bone marrow fluid is taken out for testing,” says Dr. Lee. Bone marrow biopsies are typically taken from the hip using local anesthesia.
Lymph Node Biopsy
The lymph nodes are one of the first places cancer spreads for diseases like leukemia. By taking a tiny sample of a lymph node, doctors can detect if leukemia has spread to the lymph nodes—or alternatively, if the cancer is originating in the lymph nodes (a blood cancer known as lymphoma).
Immunophenotyping
If doctors diagnose you with leukemia, they may use immunophenotyping to classify which type of leukemia you have.
“To tell if it’s a certain type of leukemia, such as a myeloid leukemia or lymphoid leukemia, we commonly test for markers that are present on the cells,” says Dr. Lee.
Flow Cytometry
This test to diagnose leukemia is used after a CBC finds an abnormally high white blood cell count. Flow cytometry helps determine if this abnormality is blood cancer—or something else.
The instrument used for this test is called a flow cytometer. It measures the percentage of certain blood cells in a sample, as well as their size, shape, and characteristics.
Cytogenetics
“Inside every cell, you have DNA. In many types of leukemias, your DNA can be abnormal,” says Dr. Lee. Cytogenetics is one test that can detect these DNA mutations associated with leukemia. It examines the chromosomes under a microscope for abnormalities.
FISH (Fluorescence in Situ Hybridization)
FISH is another type of test that checks for DNA abnormalities associated with leukemia. Like with cytogenetics, it also checks for chromosome changes, but FISH can help detect abnormalities that are not visible under a microscope.
Your doctor will choose from these test options until an accurate diagnosis can be confirmed. “It’s extremely important to know what kind of leukemia you have because treatment of leukemia differs based on what kind of leukemia you have,” says Dr. Lee.
Dr. Lee is a hematologist-oncologist at Weill Cornell Medicine and NewYork Presbyterian.
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So a CBC is a blood test that patients
often routinely obtain from their doctors.
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And it is often the first abnormality
that is detected when patients
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are diagnosed with blood cancers.
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A test called CBC is commonly done,
which stands for complete blood count.
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The key components of CBC are your white
blood cell, hemoglobin, and platelets.
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So from a CBC, a doctor can tell what the
composition of your white blood cells are,
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as well as what levels your white blood
cell and hemoglobin and platelets are.
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So leukemias come from the bone marrow.
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So a typical test that we do
to confirm the diagnosis is
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a test called bone marrow biopsy.
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It's an office procedure,
it's not a surgery.
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And basically,
a needle goes into your bone marrow and
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a small sample of bone marrow
fluid is taken out for testing.
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In addition to a bone marrow biopsy,
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you may have a lymph node biopsy,
if that's where your leukemia is involved.
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From that bone marrow biopsy, the tests
that are done that's standard workup for
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leukemia include the immunophenotyping,
flow cytometry,
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as well as cytogenetics,
FISH, and mutation testing.
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So all of these are done typically
in one package and one testing.
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To determine what kind
of leukemia you have,
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we need to do what's
called immunophenotyping.
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Your white blood cells have
different characteristics.
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And to tell if it's a certain type of
leukemia such as a myeloid leukemia or
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lymphoid leukemia, we commonly test for
markers that are present on the cells.
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And we can do that by staining the cells.
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Or we can actually stain the cells and
run it through a machine to have it
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distribute, characterize the cells, and
that test is called flow cytometry.
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Inside every cell, you have DNA.
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In many types of leukemias,
your DNA can be abnormal.
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And one test to tell an abnormality
in your leukemia is something
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called cytogenetics and FISH.
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Cytogenetics is a test where you examine
the chromosomes under a microscope and
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tell if there's any abnormal chromosomes
that are present in your leukemia cells.
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FISH stands for
fluorescence in situ hybridization,
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where you can actually
test specific probes for
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different abnormalities in the DNA that
can be found in certain leukemias.
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And that is a standard test that is
often done in diagnosis of leukemias.
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It's extremely important to know
what kind of leukemia you have,
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because treatment for leukemia differs
based on what kind of leukemia you have.
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Blood tests. Rye Brook, NY: Leukemia & Lymphoma Society. (Accessed on December 27, 2021 at https://www.lls.org/managing-your-cancer/lab-and-imaging-tests/blood-tests.)
Bone marrow tests. Rye Brook, NY: Leukemia & Lymphoma Society. (Accessed on December 27, 2021 at https://www.lls.org/managing-your-cancer/lab-and-imaging-tests/bone-marrow-tests.)
Lymph node biopsy. Rye Brook, NY: Leukemia & Lymphoma Society. (Accessed on December 27, 2021 at https://www.lls.org/managing-your-cancer/lab-and-imaging-tests/lymph-node-biopsy.)