Diagnosis is the process of finding the underlying cause of a health problem. 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 leukemia are usually done when:
- the symptoms of leukemia are present
- the doctor suspects leukemia after talking with a person about their health and completing a physical examination
- routine laboratory tests suggest a problem with the blood
Some of the same tests used to initially diagnose cancer are used to determine the stage (how far the cancer has progressed). Your doctor may also order other tests to check your general health and to help plan your 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 person has had in the past. The medical history of a person'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
- exposure to high doses of radiation
- genetic syndromes
- exposure to benzene
- previous chemotherapy or radiation therapy
- viral infections
- a family history of leukemia
- signs and symptoms
A physical examination allows the doctor to look for any signs of leukemia. During a physical examination, the doctor may:
- measure vital signs for fever, shortness of breath and rapid heartbeat
- assess the skin for bruising and paleness
- feel areas of the neck, underarm and groin for any swollen or enlarged lymph nodes
- examine the mouth for infection and bleeding or swollen gums
- feel the abdomen for enlarged organs
- examine the skeleton for tenderness or pain
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Complete blood count
A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. Leukemia is suspected when blood cell counts are abnormal and blood cells do not look normal. Abnormal blood cell counts may be due to leukemia or other conditions. Blasts (immature white blood cells) are not normally seen in the blood, so leukemia is suspected if blasts are present.
- acute leukemia:
- White blood cell counts may be low, normal or high.
- Blast cells may be present in the blood of people with acute leukemia.
- Many people with acute leukemia have neutropenia (a low neutrophil count).
- About 40% of people with acute leukemia have thrombocytopenia (a low platelet count).
- Most people with acute leukemia have anemia (low number of red blood cells).
- chronic leukemia:
- White blood cell count is high.
- Platelet count may be low.
- Anemia may be present.
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Blood chemistry tests
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities. They help to detect problems with the liver or kidney caused by the spread of leukemia cells. The following blood levels may be elevated:
- blood urea nitrogen (BUN)
- creatinine
- phosphate
- lactate dehydrogenase (LDH)
- alanine aminotransferase (ALT)
- aspartate transaminase (AST)
- uric acid
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Bleeding and clotting factors
Tests measure blood clotting factors to see how well the body can clot blood. Abnormal levels of blood clotting factors may occur with leukemia. They are measured using the following tests:
- fibrinogen level
- prothrombin time (PT) or international normalized ratio (INR)
- partial thromboplastin time (PTT)
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Cytochemistry
Cytochemistry uses stains (dyes) to identify tissue structures and cell components in blood or bone marrow cells. Certain stains are attracted to certain substances found in some types of leukemia cells. The staining results can be seen under a microscope. Cytochemistry helps determine the type of cells that are present.
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Flow cytometry
Flow cytometry is a laboratory test that is used to sort, count and examine microscopic particles (such as cells or DNA). Cells are measured by staining them with a light-sensitive dye, placing them in fluid and passing them through a laser beam. The laser makes these cells give off a light that is measured and analyzed by a computer. Flow cytometry helps determine the types of cells that are present.
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Immunohistochemistry
Like flow cytometry, immunohistochemistry (or immunocytochemistry) treats a sample of cells from blood or bone marrow with special antibodies. Instead of using a laser and computer, chemicals are added that make the cell change colour if a certain antibody attaches to it. The change in colour can only be seen under a microscope. Immunohistochemistry helps determine the types of cells that are present.
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Cytogenetics
Cytogenetic techniques test a sample of blood or bone marrow to help identify segments of individual chromosomes (like bar codes) and tell them apart. Cytogenetic techniques show chromosomal abnormalities, which help to confirm the diagnosis and identify the type of leukemia. The results are also helpful in planning treatment and predicting response to treatment. Results for cytogenetic testing are usually available within 3–4 weeks.
Chromosome changes that occur in some people with leukemia include:
- translocations – part of a chromosome attaches to part of a different chromosome
- inversions – part of a chromosome breaks off, flips end-to-end, and rejoins the same chromosome
- loss or gain of a chromosome number
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Fluorescent in situ hybridization (FISH)
Fluorescent in situ hybridization (FISH) is similar to cytogenetic testing and can be used to look for specific changes in chromosomes in blood or bone marrow cells. Some abnormalities that are too small to be found with standard cytogenetic testing can be found using FISH.
FISH uses special dyes that attach only to specific parts of certain chromosomes. It is very accurate and results are usually available within a couple of days.
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Polymerase chain reaction
Polymerase chain reaction (PCR)and reverse transcriptase polymerase chain reaction (RT-PCR) are sensitive genetic tests used to find specific abnormalities in blood or bone marrow cells. Abnormalities can be found even if very few leukemia cells are present in a tissue sample.
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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 the laboratory. The pathology report from the laboratory will confirm whether or not the person has leukemia and, if so, what type of leukemia.
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Lumbar puncture
A lumbar puncture (LP) removes a small amount of cerebrospinal fluid (CSF) from the space around the spine for examination under a microscope. CSF is the fluid that surrounds the brain and spinal cord. A lumbar puncture is done to see if cancer has spread to the spinal fluid.
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Lymph node biopsy
A lymph node biopsy is a type of surgical biopsy. It is called an excisional biopsy because the lymph node is completely removed. The lymph node is then examined under a microscope to identify the type of cells and the pattern in which they are growing.
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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 look for:
- enlarged mediastinal lymph nodes (lymph nodes in the centre of the chest)
- enlarged thymus gland
- buildup of fluid around the lungs
- pneumonia (lung infection)
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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. It may be used to show enlarged lymph nodes around the heart, near the trachea (windpipe) or in the back of the abdomen.
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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. It is helpful for looking at the brain and spinal cord. It is most often used when there is concern that the leukemia has spread to the brain.
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Ultrasound
Ultrasound uses high-frequency sound waves to make images of structures in the body. It is used to see if internal organs, such as the kidneys, liver, or spleen, have been affected by leukemia.
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See a list of questions to ask your doctor about diagnostic tests.