Laboratory diagnosis of Leukemia

Tests used for diagnosing leukemia

If you’re concerned you may have leukemia or are experiencing symptoms associated with leukemia, a physical exam is often the first method your doctor utilizes to see what’s going on.

The physical exam may be focused on looking or feeling for swelling in the lymph nodes, liver and spleen. Your eyes, mouth and skin may also be examined. Your doctor may also be on the lookout for signs of infection and bruises, as frequent infections, widespread bruises and easy bleeding are associated with some types of leukemia.

A nervous system exam may also be performed, which often involves checking your balance, sensation (touching different areas of the body to make sure you have proper sensation) and reflexes (tapping certain body parts with a small rubber hammer).

 

Lab tests

Laboratory tests, and specifically blood tests, are among the most important diagnostic tools for leukemia. For some types of leukemia, such as chronic lymphocytic leukemia, blood tests may be the only test needed to confirm the diagnosis (but other tests may be used to find out more about the cancer).

To officially diagnose other types, such as acute lymphocytic leukemia, blood tests are typically followed by bone marrow tests. Most of the time, blood tests, and specifically a test called a complete blood count, are the first step in the diagnostic process.

Complete blood count (CBC): This blood test measure the amount of red blood cells, white blood cells and platelets in the blood.

Differential: A differential, or diff, analyzes how many of each type of white blood cell are present in your blood.

Peripheral blood smear: This blood test requires just one drop of blood, which is smeared or spread out across a surface and then analyzed under a microscope. The laboratory technician looks at the appearance of the blood cells, as certain changes in the look of these cells may point toward leukemia.

Leukemia blood test results

The results of a CBC, diff and peripheral blood smear are an essential part of diagnosing leukemia and, if present, determining the type of leukemia. These blood tests tend to reveal different findings depending on the type of leukemia. The findings associated with some of the main leukemia types are summarized below.

• Acute myeloid leukemia (AML): Blood tests of people with AML tend to reveal high levels of immature white blood cells and low levels of red blood cells and platelets. Among the white blood cells, many are myeloblasts, a type of white blood cell that isn’t normally found in healthy blood.
• Chronic lymphocytic leukemia (CLL): The blood of people with CLL contains high levels of lymphocytes (a type of white blood cell). Under a microscope, these cells don’t look like normal, healthy cells. The number of platelets and red blood cells may be low.
• Chronic myeloid leukemia (CML): People with CML tend to have high levels of white blood cells, many of which are myeloblasts. The cells appear abnormal under a microscope. Red blood cells and platelet counts may be low.
• Acute lymphocytic leukemia (ALL): Blood tests of people with ALL often reveal high levels of lymphoblasts (immature white blood cells) and low levels of red blood cells and platelets.

Flow cytometry

A flow cytometry test may provide valuable insight into whether the tumor cells contain a normal or abnormal amount of DNA, and the relative rate at which the tumor is growing.

This test is a very accurate indicator in determining the patient’s exact kind of lymphoma or leukemia. The test may be performed on bone marrow cells (taken during a biopsy) or blood cells (taken during a blood test). These cells are exposed to special antibodies (proteins), which will attach to specific proteins on the cells that match them. Cancer is suspected if the antibodies attach to most cells in the sample, as this indicates that the cells originated from one abnormal cell. Cancer is unlikely if different antibodies attach to different cells in the sample, as this means that there are a variety of cell types.

The process may also reveal how much DNA is in cancer cells, which indicates whether the cancer is likely to grow quickly or slowly.

Biopsy

A biopsy is used to determine the type of leukemia, the growth rate of the tumor, and whether the disease has spread. Common biopsy procedures for leukemia include:

Bone marrow biopsy removes a sample of bone marrow. Since leukemia begins in bone marrow, examining these cells is an important part of diagnosing leukemias. There are two types of procedures used to extract a bone marrow sample, and they are often performed simultaneously.

• A bone marrow aspiration collects a sample of liquid bone marrow. In this procedure, you lie on a table. Your doctor uses a needle to inject a numbing medication into the area of bone being tested (usually your hip bone). Then, the doctor inserts a hollow needle into your bone and extracts a sample of liquid bone marrow from inside.
• A bone marrow biopsy collects a small piece of the bone and bone marrow. Typically performed after a bone marrow aspiration, a bone marrow biopsy is a procedure that removes a small sample of your bone and a little bone marrow. This procedure also involves inserting a needle into your bone, but the needle is slightly larger. The needle is twisted as it’s inserted into your bone to help collect the sample.
• These procedures may come with brief pain or pressure in the area. However, the numbing medication helps minimize pain.

• For most types of leukemia—such as acute lymphocytic leukemia, acute myeloid leukemia and chronic myeloid leukemia—diagnosis typically requires the bone marrow to be tested. Other types, such as chronic lymphocytic leukemia, may be diagnosed using blood tests alone, but some patients with this cancer may still undergo a bone marrow biopsy to assess how advanced the cancer is before beginning treatment.

Lymph node biopsy removes all or part of a lymph node. This procedure is rarely needed to diagnose leukemia, as tests on the blood and bone marrow are much more important. When it’s used, however, it’s typically done because a lymph node has increased in size after diagnosis, raising concern that the cancer may have become more aggressive. There are two types of lymph node biopsies: excisional (to remove an entire lymph node) and incisional (to remove part of a lymph node). If you need to have a lymph node deep inside the body (or part of a lymph node) removed, you may be given general anesthesia for the procedure. To remove lymph nodes that are more easily accessible, you may only need local anesthetic to numb the area.

Imaging and other tests for leukemia

Imaging tests

These procedures may provide information about the extent of leukemia in the body, and the presence of infections or other problems. The following imaging tests may be used to help formulate a leukemia diagnosis:

• X-rays are used to produce images of the inside of your body. As with some leukemia patients, you may need regular X-rays of your chest to see whether you have a lung infection.
• Computed tomography (CT) scans use X-rays to create more in-depth and detailed pictures of the body. CT scans help reveal swelling in the lymph nodes and organs. While these scans aren’t typically necessary for diagnosing leukemia, doctors sometimes use them to find out whether there’s cancer in an organ, such as the spleen.
• A positron emission tomography (PET) scan may be used together with a CT scan to produce more precise images of where there is cancer in your body. Before a PET scan, the doctor injects a substance that disseminates in your body and lands in areas where there are cancer cells. These areas are highlighted in the images created by the scan, indicating where there may be cancer. The images produced by the CT scan are more detailed than a PET scan alone, which is why they may be combined.
• Magnetic resonance imaging (MRI) scans also create detailed pictures of your body. With leukemia, you may need an MRI scan if you’re having symptoms that suggest the cancer has spread to the brain or spinal cord.
• Ultrasounds produce pictures by sending sound waves into the body that echo when they bounce off organs and other structures. This imaging test may be helpful to see whether your organs (such as the liver, spleen or kidneys) or lymph nodes are enlarged, potentially indicating the presence of cancer in those areas.
• A 2D echocardiogram produces images of the heart using sound waves. This imaging test is often used after you’ve been diagnosed with acute myeloid leukemia, and before treatment begins. The standard treatment for AML involves a chemotherapy drug that may cause heart problems. If you have this type of cancer, you usually need to have your heart function assessed with an echocardiogram to ensure safe treatment decisions are made.

Pulmonary function test

A pulmonary function test may be used to assess your lung function before or after treatment. It may help you and your care team know whether your lungs are strong enough for treatments and/or how current treatments might be affecting your lungs. There are different ways to do this, including:

• Spirometry
• Lung plethysmography
• Lung diffusion testing

A spirometry test requires you to breathe into a tube, and a computer measures how much air is exhaled with every breath. Lung plethysmography uses a machine to assess how much air you breathe in when you inhale and then with what force you breathe out when you exhale. Lung diffusion testing involves inhaling a gas through a tube, waiting a few seconds, and then exhaling. The exhaled air is kept in a tube that your doctor examines.

Lumbar puncture

Also known as a spinal tap, this test may be required to determine the extent of leukemia. During this procedure, a needle is used to collect cerebrospinal fluid from the lower back. Lumbar punctures may also be used to inject medications, such as chemotherapy drugs, to treat the disease.

 

 

 

.