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Diagnosis of childhood leukemia
Diagnosing childhood leukemia usually begins with a visit to your child’s doctor. The doctor will ask you about any symptoms your child has and do a physical exam. Based on this information, the doctor may order tests to check for childhood leukemia or other health problems. If the doctor suspects leukemia, your child may be taken care of by a healthcare team that specializes in treating children with cancer.
The process of diagnosis may seem long and frustrating. It’s normal to worry, but try to remember that other health conditions can cause similar symptoms as childhood leukemia. It’s important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of childhood leukemia.
The following tests are commonly used to rule out or diagnose childhood leukemia. Many of the same tests used to diagnose cancer are used to find out the stage, which is how far the cancer has progressed. Your doctor may also order other tests to check your child’s general health and to help plan treatment.
Your child’s health history is a record of symptoms, risk factors and all the medical events and problems the child has had in the past. In taking a health history, your child’s doctor will ask questions about a family history of cancer and your child’s personal history of certain genetic conditions, including:
- Down syndrome
- Bloom syndrome
- Fanconi anemia
- neurofibromatosis type 1 (von Recklinghausen disease)
- Wiskott-Aldrich syndrome
- Klinefelter syndrome
- Li-Fraumeni syndrome
- Shwachman-Diamond syndrome
A physical exam allows the doctor to look for any signs of childhood leukemia. During a physical exam, the doctor may:
- measure vital signs to check for fever, shortness of breath and rapid heartbeat
- check the skin for bruising and paleness
- feel areas of the neck, underarm and groin for any swollen or enlarged lymph nodes
- check the mouth for infection, bleeding or swollen gums
- examine the testicles for swelling
- feel the abdomen for enlarged liver or spleen
- examine the skeleton for tenderness or pain
Find out more about physical exam.
A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. A CBC is done to see how well the bone marrow is working and to check for anemia. Childhood leukemia may be suspected if:
- the blood cell counts are outside normal ranges
- there are immature blood cells, or blasts, in the blood (blasts are normally only found in the bone marrow)
- the white blood cell (WBC) count is low or high
- the number of platelets is low
Find out more about complete blood count (CBC).
Leukemia can cause abnormal levels of blood clotting factors, which can affect how well the body can clot blood. The following tests may be done to measure blood clotting factors:
- fibrinogen level
- prothrombin time (PT) or international normalized ratio (INR)
- partial thromboplastin time (PTT)
During a bone marrow aspiration and biopsy, cells are removed from the bone marrow so they can be tested in a lab. The results of the bone marrow aspiration and biopsy will confirm whether or not the child has leukemia.
The samples collected during bone marrow aspiration can also be used for other tests such as cytochemistry, immunophenotyping and chromosome and molecular genetic analyses. These tests help doctors identify the type of leukemia and plan the best treatments for the child.
Find out more about bone marrow aspiration and biopsy.
Cytochemistry uses stains, or dyes, to identify tissue structures and components in blood or bone marrow cells. Certain stains are attracted to certain substances found in some types of blasts, or leukemia cells. The staining results can be seen under a microscope. Cytochemistry helps doctors determine the type of cells that are present.
Immunophenotyping is the study of proteins expressed by cells. It is used to determine the type or subtype of leukemia.
Immunophenotyping uses a very specific antigen-antibody reaction to identify proteins in tissues or cells. It uses monoclonal antibodies marked with a fluorescent or specific enzyme label that binds only to specific antigens (proteins). The fluorescent or enzyme label allows doctors to see the blasts, or leukemia cells.
The 2 most common methods used in immunophenotyping are:
Immunohistochemistry uses a microscope to view the fluorescent labels. It also allows doctors to examine cells and what is around them.
Flow cytometry is a technique used to sort and classify cells using fluorescent labels on their surface. It allows doctors to view many antibodies at the same time. The cells are exposed to a laser, which makes the cells give off a light that is measured and analyzed by a computer. It allows data to be collected rapidly from thousands of cells in a single sample.
Flow cytometry helps to define unique features of blasts, or leukemia cells. These features can help doctors form a prognosis and measure response to treatment using minimal residual disease (MRD). MRD describes blasts in the bone marrow that can’t be found using standard lab tests, such as microscopy, but are found using more sensitive tests, such as flow cytometry or polymerase chain reaction (PCR).
Cytogenetics is the analysis of a cell’s chromosomes, including the number, size, shape and how they are arranged. Cytogenetic techniques show chromosomal abnormalities, which help doctors confirm the diagnosis and identify the type or subtype of leukemia. The results of cytogenetic studies also help doctors plan treatment and predict how well the treatment will work.
Some major chromosomal abnormalities can be found by looking at cells under a microscope. But most changes in DNA need a closer analysis through other molecular techniques. These molecular techniques include the following.
Fluorescent in situ hybridization (FISH)
Fluorescent in situ hybridization (FISH) is a molecular genetic test used to identify chromosomal abnormalities and other genetic changes in the leukemia cells, or blasts. It uses special DNA probes labelled with fluorescent dyes. FISH is used to diagnose leukemias that look the same but that have different genetic abnormalities and may need to be treated differently.
Polymerase chain reaction (PCR)
Polymerase chain reaction (PCR) is a method used to make many copies of a particular gene segment so that it can be tested in the lab. PCR is used to find DNA mutations, inversions or deletions that are associated with certain types of leukemia. It is useful in diagnosing and determining the prognosis for a specific type of leukemia.
A lumbar puncture, or spinal tap, involves removing a small amount of cerebrospinal fluid (CSF) from the spine. CSF is the fluid that surrounds and helps protect the brain and spinal cord. The CSF fluid removed during lumbar puncture is examined under a microscope to see if cancer has spread to the central nervous system (CNS).
Find out more about lumbar puncture.
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs, such as the liver and kidneys, are working and can help find abnormalities. They may be used to set a baseline before treatment for leukemia begins. Blood chemistry tests used to diagnose or stage childhood leukemia include:
Blood urea nitrogen (BUN) and creatinine may be measured to check kidney function.
Alanine aminotransferase (ALT), aspartate transaminase (AST) and alkaline phosphatase are liver enzymes that are measured to check liver function.
Lactate dehydrogenase (LDH) may be measured to check for tissue damage. LDH may be high due to leukemia or other conditions.
Phosphate levels in blood may be measured to check for problems with kidney, liver or bone.
Uric acid levels in the blood may be elevated with leukemia or other conditions.
Electrolytes, such as sodium and potassium, may be measured as part of routine testing and can be used to check for a number of conditions.
Find out more about blood chemistry tests.
During a testicular biopsy, tissues or cells are removed from the testicle so they can be tested in a lab. The pathology report from the lab will confirm whether or not leukemia cells, or blasts, are present in the sample. A testicular biopsy may be done if a child has an enlarged testicle.
Find out more about biopsy.
An x-ray uses small doses of radiation to make an image of the body’s structures on film. A chest x-ray is used to check:
- the child’s airway before sedation for bone marrow aspiration and biopsy
- for a lung infection
- for an enlarged thymus
- for enlarged lymph nodes in the chest
Find out more about x-ray.
A computed tomography (CT) scan uses special x-ray equipment to make 3-D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures.
A CT scan is used to check for:
- enlarged lymph nodes in the chest
- enlarged spleen or liver
- infection in the lung
Find out more about CT scan.
Ultrasound uses high-frequency sound waves to make images of structures in the body. It is used to check if organs that can be affected by leukemia, such as the kidneys, spleen, liver or testicles, are enlarged.
Find out more about ultrasound.
Magnetic resonance imaging (MRI) uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-D pictures.
MRI may be used to look for leukemia that has spread to the brain. But spread to the brain is very rare.
Find out more about MRI.
Questions to ask your healthcare team
Find out more about how to help a child cope with tests and treatment and see a list of questions to ask your child’s doctor about diagnosis.
His amazing career and legacy live on today, inspiring a new generation of scientists who are discovering new ways to harness the power of medical imaging to improve cancer diagnosis and treatment.
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