A series of blood tests, procedures, and imaging tests can help diagnose acute myeloid leukemia (AML). Additionally, these tests can also determine its subtype and help identify the best treatment options available.
AML is a blood cancer that begins in the bone marrow. It occurs due to atypical blood-forming cells that are not fully developed and do not work properly. They grow and divide too fast and build up in the bone marrow, so there is not enough space for typical blood cells. They eventually spread to other parts of the body.
Doctors can diagnose AML by examining blood and bone marrow samples using various tests. Other tests, such as lumbar puncture and imaging tests, can also help check its spread and screen for infections and other problems.
In this article, we will discuss the different tests that can diagnose and stage AML.
A doctor may begin the diagnostic process by taking someone’s medical history. They will ask questions about the person’s symptoms, risk factors relating to AML, and other health conditions.
The doctor will also perform a physical exam and look for physical signs of the condition, including:
- enlarged lymph nodes
- spleen and liver enlargement
- areas of bruising and bleeding
- possible signs of infection
If they suspect someone has AML, they will order a range of tests and refer them to a hematologist, a doctor specializing in blood diseases.
The initial step in AML diagnosis is extracting a
A person will undergo two bone marrow tests, which healthcare professionals typically perform simultaneously, to obtain two types of bone marrow samples. Doctors call these tests bone marrow aspiration and a biopsy. For the former, a doctor inserts a thin, hollow needle into the hipbone and withdraws some bone marrow. A biopsy involves using a slightly larger needle to take a small piece of bone.
Aside from blood and bone marrow samples, they may also acquire other cell and tissue samples to monitor the condition and help guide treatment. For example, a lumbar puncture, or spinal tap, is not a standard test for diagnosing AML. However, doctors may perform one to remove a sample of cerebrospinal fluid to check if the leukemia cells have spread into the brain and spinal cord.
A person’s samples may undergo one or more of the following tests to diagnose AML or determine their AML subtype.
Complete blood count (CBC)
People with AML have an excess of immature white blood cells (WBCs) in their blood. A CBC measures the number of red blood cells, WBCs, and platelets in the blood. A CBC with differential screening also determines the number of different types of WBCs in the sample.
Peripheral blood smear
This test looks at the sample under a microscope to examine the cells’ number, size, and shape. People with AML often have an excess of immature white blood cells, which look different from mature white blood cells and are not usually present in the blood.
Hematopathologists, who are doctors trained in identifying blood diseases, will study the cell sample under a microscope to classify them into specific types. They will check if they are mature or immature — the latter are known as blast cells. For doctors to make a diagnosis of AML, there should be
Leukemia cells have distinct antigens on their surfaces, which distinguishes them from healthy cells. Flow cytometry, or immunophenotyping, detects the characteristics of the cells in the sample, including their number and the specific markers on their cell surface.
The test involves treating the cells with antibodies that only stick to specific markers observable on leukemia cells. An instrument called a flow cytometer passes a laser beam on stained cells and detects cells with antibodies attached to them.
Learn more about different AML types.
Like flow cytometry, an immunohistochemistry test treats cell samples with antibodies. However, it uses a microscope to identify and localize the antigens in the cells.
This test involves exposing cell samples to chemical stains that react only with some types of leukemia cells.
The stains cause color changes, which doctors can see under the microscope to identify the type of leukemia cells someone has. For example, one stain
Cancer can change the genes of affected cells. Molecular tests look for changes in the genes and chromosomes in leukemia cells. This can help identify specific types of AML, giving insights into the suitable treatment options and outlook for an individual. Molecular tests include:
- Cytogenetics: This test looks for chromosomal abnormalities in cell samples.
- Fluorescence in site hybridization: This technique uses fluorescent dyes that only attach to specific chromosomes or genes to find changes under a microscope.
- Polymerase chain reaction: This test is suitable for detecting gene changes in only a few cells, making it beneficial in measuring leukemia cells after treatment.
While doctors do not use imaging tests in making an AML diagnosis, they can help determine the person’s general health, identify the cause of symptoms, and look for infections.
Doctors can use chest X-rays to check for a person’s lung and heart health before deciding on the most appropriate treatment for them. X-rays can also
CT scans use X-rays to create detailed, three-dimensional images of the body. This can help detect enlarged organs or lymph nodes in the body and infections in the organs. It can also help guide a biopsy needle toward a suspected atypical mass, such as an abscess.
PET/ CT scans
PET/CT scans acquire images of tissues and organs inside the body according to the detected radioactive activity. For the procedure, a person will receive a small amount of radioactive sugar. Cancer cells tend to absorb more of the substance because they use energy to grow and divide rapidly.
A 2019 study found that PET/CT scans are highly sensitive in detecting small sites of cancer spread that CT scans may miss.
MRI scans use magnetic fields to produce detailed images of the body. Doctors do not typically use them for people with AML, but they may use them if symptoms suggest leukemic cells are in the brain.
Ultrasound scans use sound waves to create pictures of internal organs on a screen. This can help detect enlarged lymph nodes and organs. Doctors can also use it to guide a needle during a needle biopsy.
Doctors can use a series of tests to diagnose AML. These tests can identify if a person has AML, the type of leukemia cells they have, and provide information about their outlook and suitable treatment options. Doctors may also repeat these tests to monitor someone’s response to treatment.
Other tests, such as imaging scans, can help assess a person’s general health, look for infections, and identify the causes of their symptoms.