Diagnosis is the process of finding the underlying cause of a health problem. If cancer is suspected, the healthcare team will confirm if it is present or not, and what type of cancer it is. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other possible reasons for a health problem before making a cancer diagnosis.
Diagnostic tests for childhood leukemia are usually done when:
- the symptoms of leukemia are present
- the doctor suspects leukemia after completing a physical examination
- blood tests suggest an abnormality
Many of the same tests used to initially diagnose cancer are also used to determine the stage (how far the cancer has progressed). The doctor may also order other tests to check the child's general health and to help plan the child's treatment. Tests may include the following.
Medical history and physical examination
The medical history is a record of present symptoms, risk factors and all the medical events and problems a child has had in the past. The medical history of a child's family may also help the doctor to diagnose leukemia.
In taking a medical history, the doctor will ask questions about:
- a personal history of certain genetic conditions
- a family history of cancer
- signs and symptoms
A physical examination allows the doctor to look for any signs of leukemia. During a physical examination, the doctor may:
- feel the abdomen for enlarged liver or spleen
- check for enlarged lymph nodes
- exam the testicles for swelling
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Complete blood count (CBC)
A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. It is used to see how well the bone marrow is working and to check for anemia. Leukemia may be suspected if the blood cell counts are outside normal ranges or if the blood cells look abnormal.
- A low or high white blood cell (WBC) count may indicate leukemia.
- A low number of platelets may indicate leukemia.
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Bone marrow aspiration and biopsy
During a bone marrow aspiration and biopsy, cells are removed from the bone marrow so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not the child has leukemia and, if so, what type of leukemia.
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Cell and tissue tests
There are a number of tests that can be used to examine cells or tissues to diagnose leukemia.
Flow cytometry
Flow cytometry is a technique used to sort and classify cells by using fluorescent markers on their surface. It is used to make a diagnosis of leukemia and to establish the type of leukemia.
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 cancer cells. It uses special DNA probes labelled with fluorescent dyes. FISH is used to diagnose leukemias that may look similar but have different genetic abnormalities and may need to be treated differently.
Polymerase chain reaction (PCR)
Polymerase chain reaction (PCR) is a method used to produce many copies of a particular gene segment so that it can be tested in the laboratory. PCR is used to detect DNA mutations, inversions or deletions associated with certain leukemias. It is useful in diagnosing and in determining the prognosis for a specific type of leukemia.
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Lumbar puncture
A lumbar puncture involves removing a small amount of cerebrospinal fluid (CSF) from the spine for microscopic examination. A lumbar puncture is done to see if cancer has spread to the spinal fluid.
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Blood chemistry tests
Blood chemistry tests measure different chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities. They may be used as a baseline for treatment of leukemia.
- Kidney function tests show how well the kidneys are working.
- Liver function tests show how well the liver is working.
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Testicular biopsy
During a testicular biopsy, tissues or cells are removed from the testicle so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample. A testicular biopsy may be done if the child has an enlarged testicle.
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Chest x-ray
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
- check for a mass in the chest
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Computed tomography (CT) scan
A CT scan uses special x-ray equipment to make 3-dimensional 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 may be used to look for signs of leukemia, such as a mass of lymph nodes in the chest.
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Ultrasound
Ultrasound uses high-frequency sound waves to make images of structures in the body. An ultrasound may be used to check if organs that can be affected by leukemia, such as the kidneys, spleen or liver, are enlarged.
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Magnetic resonance imaging (MRI)
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-dimensional pictures. MRI may be used to look for leukemia that has spread to the brain, but this is very rare.
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See a list of questions to ask your child's doctor about diagnostic tests.