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When your child’s doctor orders a blood test, they choose from a list of chemical studies to be performed in a laboratory on your blood sample. These lab tests can provide important clues about what's going on inside your child’s body.
If the doctor suspects your child may have blood cancer, they may test your child’s blood to:
- Measure the number of red cells, white cells, and platelets
- Detect biomarkers or molecules that indicate either a normal or an abnormal process in the body that may indicate cancer activity
- Examine various chemicals that can indicate how other parts of your body are functioning, including your liver, kidney, heart, and lungs
About 5 percent of healthy people will have test results outside of the "normal" range. If one or more of your child’s blood cell counts is higher or lower than normal, their doctor will try to find out why. Many noncancerous conditions can contribute to low or high blood cell counts. Talk to your child’s doctor about other possible causes.
Understanding blood counts
Blood cell counts give the doctor important clues about the state of your child’s health before, during, and after treatment. Blood counts alone can't determine whether your child has a blood cancer, but they can alert the doctor if further testing is needed.
A complete blood count (CBC) is the number and types of cells circulating in the blood. Your child’s CBC is measured using laboratory tests that require a small blood sample.
Blood is composed of several types of cells:
- Red cells, sometimes referred to as erythrocytes, pick up oxygen as blood passes through the lungs and releases it to the cells in the body
- White cells, sometimes referred to as leukocytes, help fight bacteria and viruses
- Platelets help the blood clot in response to a cut or a wound
View the interactive 3D model to help you visualize and better understand the procedure. Click or tap the "Interact in 3D" button to begin.
A CBC also tests hemoglobin and hematocrit:
- Hemoglobin is a protein used by red cells to distribute oxygen to other tissues and cells in the body
- Hematocrit refers to the amount of the blood that's occupied by red cells
Learn more about the blood, bone marrow, and lymphatic system in children and teens.
Normal blood counts
Normal blood counts fall within a range established by testing healthy men and women of all ages. The cell counts are compared to those of healthy individuals of similar age and sex. Nearly all lab reports include a "normal" range or high and low "values" to help you understand test results.
| Red cells | White cells | Platelets | Hematocrit1 | Hemoglobin1 |
| Children2 | 4.0 to 5.5 million | 5,000 to 10,000 | 150,000 to 400,000 | 32 to 44 | 9.5 to 15.5 |
| Women3 | 4.2 to 5.4 million | 4,500 to 11,000 | 150,000 to 400,000 | 37 to 47 | 12 to 16 |
| Men | 4.7 to 6.1 million | 5,000 to 10,000 | 150,000 to 400,000 | 42 to 52 | 14 to 18 |
| 1The ratio of hematocrit to hemoglobin is about 3 to 1. 2These ranges are for children from infancy to adolescence; speak with your doctor to find out specific values for infants and young children. 3Normal ranges for women who are pregnant differ from these ranges. | |||||
White cell differential
Differential count, sometimes referred to as a "diff," is a breakdown of the different types of white cells. A white cell (WBC) differential also checks whether white cells appear normal. The types of white cells and the approximate percentage they make up in the blood are:
- Neutrophils (55% to 70%)
- Band neutrophils (0% to 3%)
- Lymphocytes (20% to 40%)
- Monocytes (2% to 8%)
- Eosinophils (1% to 4%)
- Basophils (0.5% to 1%)
Until children are more than 4 years old, they have a higher percentage of lymphocytes in their blood than adults do.
How blood cancers affect blood counts
Blood cancers can affect blood cell counts in a number of ways, by either lowering or increasing measurements. If your child is currently receiving cancer treatment such as chemotherapy, drug therapy, or radiation, their blood counts will be affected. Blood counts usually return to normal after treatment is complete.
Should you keep track of a child’s blood counts?
Some people want to know the results of their child’s blood count tests so they can take preventive measures to protect their health or to know what's causing their symptoms. For example:
- If your child has anemia as a result of low red cell counts, you'll understand why they have low energy levels or are unable to carry out everyday tasks
- If your child has low white cell counts and develops a fever, you'll know to contact your doctor promptly
- If your child’s platelet counts are too low, they can bleed or bruise easily, so they may choose to avoid activities that have a risk of injury
How are blood tests done?
Ask your child’s doctor if they need to follow any special instructions. For example, your child’s doctor may ask them to fast (not eat or drink) before having blood taken. Blood tests are usually done in one of two ways:
- A needle is inserted into a vein (usually in the fold of the arm) and blood is withdrawn. Your child may feel a slight pinprick. Your child’s sample is placed in a test tube and sent to a laboratory for analysis.
- If only a small amount of blood is needed, the doctor can obtain blood by simply pricking your child’s finger. Your child’s blood sample is placed on a glass laboratory slide to be examined under a microscope or in a test tube for analysis.
Different types of blood tests tor cancer
There are different types of blood tests that help doctors make a blood cancer diagnosis and determine a course of treatment. Learn more about the different types of blood tests below:
Your child’s blood chemistry is examined using a group of tests called "chemistry panels," which provide information about general health. Depending on the type of panel, these tests can measure:
- Electrolyte balance (such as sodium or potassium)
- Protein (such as albumin, beta2 -microglobulin, immunoglobulins [IgM, IgG and others], and lactate dehydrogenase [LDH])
- Blood glucose (sugar)
- Cholesterol
- Chemical substances that indicate liver and kidney function
- Antibodies, including those developed from vaccinations (such as poliovirus antibodies)
- Hormones (such as thyroid hormone)
- Minerals (such as iron, calcium, or potassium) and vitamins (such as B12 or folate)
How is a blood chemistry assessment done?
Your child may be asked to fast before taking a blood test. Once your child’s blood is drawn, it's placed in a tube(s) and usually left to clot. The fluid portion of the blood that remains after clotting, called the serum, is used for various chemical studies.
What do the results mean?
The results give the doctor information about your child’s overall health and identify potential problems that may need treatment. Higher levels of certain blood proteins can be signs of disease severity (for example, tumor size and growth rate). High levels of uric acid can sometimes indicate disease as well.
Your child’s doctor may order a blood smear (also called a peripheral blood smear or manual differential) if your child’s CBC results are abnormal or unclear, or if the doctor thinks a disorder or disease may be disrupting normal blood cell production. This test helps determine whether red cells, white cells, and platelets are normal in appearance and number. It's also used to determine the proportion of each type of white cell relative to the total white cell count. The results also help your child’s doctor monitor cell production and cell maturity before and during blood cancer therapy.
How Is a blood smear done?
A single drop of blood is spread on a glass slide, dried, and then stained with a special dye. The sample is then examined under the microscope to calculate the number of each type of blood cell. The doctor also compares the size, shape, and general appearance of the sampled cells to "normal" cells.
What do the results mean?
This test can show the presence of abnormal or immature cells, which may indicate an underlying condition, provide information about its severity, and suggest the need for further testing.
A complete blood count (CBC) is a common test that gives a general picture of health. A CBC measures the number of red cells, white cells (neutrophils, eosinophils, basophils, monocytes and lymphocytes), platelets, and levels of hemoglobin and hematocrit in your child’s blood. Many health conditions cause increases or decreases in blood counts. Your child’s doctor may order a CBC regularly to monitor their condition or track their response to treatment.
How is a CBC done?
A blood sample is placed in a test tube containing an anticoagulant (to prevent clotting) and sent to a laboratory to be examined by a pathologist. Dyes are added to the blood sample so that different types of blood cells are noticeable. The slide with the sample of blood cells is examined under a microscope to count the number of cells and see whether they're normal or, if abnormal, the nature of the changes.
What do the results mean?
Normal ranges vary slightly among different labs, so ask your child’s doctor to review the results with you. Results above or below normal ranges may signal health problems.
Samples of fluid, tissue, and cells are examined under a microscope to look for chromosome changes. Cytogenetic analysis detects chromosome alterations and, in some cases, may identify the actual genes that have been affected. The individual who prepares and examines the chromosomes and interprets the results is called a “cytogeneticist.”
How is a cytogenetic analysis done?
Cell samples are collected through blood or bone marrow tests.
What Do the Results Mean?
The findings help healthcare professionals diagnose specific types of blood cancers, determine treatment approaches, and monitor the response to treatment.
A test that can help identify cancer subtypes and risk factors, gene expression profiling is not generally used in clinical practice and these tests are still mostly used as research tools. This test uses a method called “microarray analysis” to identify combinations of genes that are turned off or on in response to specific conditions.
How is gene expression done?
Genes are collected from blood or tissue samples.
What do the results mean?
The test findings may allow for more accuracy classifying tumors and help doctors to predict how patients will respond to treatment, as well as which patients may be at increased risk for disease relapse.
Immunophenotyping identifies a specific type of cell in a sample of blood, bone marrow, or lymph node cells. This procedure can be important in determining the best treatment. For example, immunophenotyping can distinguish myeloid leukemic cells from lymphocytic leukemic cells, normal lymphocytes from leukemic lymphocytes, and B-cell lymphocytes from T-cell lymphocytes. Immunophenotyping also reveals whether your child’s cells are monoclonal (derived from a single malignant cell).
Flow cytometry can identify the type of cells in a blood or bone marrow sample, including the types of cancer cells. It detects types of cancer cells based on either the presence or the absence of certain protein markers (antigens) on a cell’s surface. The most common use of flow cytometry is in the identification of markers on cells, particularly in the immune system (called immunophenotyping).
How is flow cytometry done?
A sample of cells from the blood or a bone marrow biopsy is treated with special antibodies created in the laboratory. Each antibody only sticks to certain types of cells that have the antigens that fit with it. The cells are then passed through a laser beam. If the cells have antibodies attached to them, they will give off light that is then measured and analyzed by a computer.
What do the results mean?
Flow cytometry can provide information that is used to diagnose, stage, and monitor blood cancers. It can also be used to test for minimal residual disease (MRD), the number of cancer cells remaining in the body after treatment. Detecting MRD helps doctors to determine which patients need additional treatment and which patients do not. Evaluating for MRD in your child’s blood may also help their doctor to decide how to monitor the child’s disease and how to follow up after their treatment is complete.
A karyotype test uses a map of the 46 human chromosomes of a cell to identify and evaluate changes to the expected chromosome arrangement, size, shape, and number in a sample of blood or bone marrow cells. In some cases, a dye called Giemsa may be used as a stain to make the banding pattern of chromosome pairs easier to see. This is also referred to as "G-banding." The findings can help your child’s doctor develop a more specific treatment plan.
Molecular profiling involves the use of various technologies to understand the underlying characteristics that are found in cancer cells and can be used to identify specific cancer biomarkers that are associated with response, resistance, or lack of response to certain treatment approaches.
First a biopsy procedure obtains a patient's sample from a tumor tissue, bone marrow, lymph node (for some blood cancers), or peripheral blood, in cases when tumor cells are circulating. The sample is then sent to a laboratory, where it undergoes various molecular profiling tests to identify the unique biomarkers that correspond to the patient's cancer. A cancer biomarker is associated with the presence of cancer in the body. A biomarker can be produced by the tumor itself, or it may be a specific response by the body to the presence of cancer.
The ultimate goal of molecular profiling is the development of individualized, highly targeted, and effective therapies that can improve patient outcomes.
Types of molecular profiling tests
- Fluorescence in situ hybridization (FISH): This test is performed on your child’s blood or bone marrow cells to detect chromosome changes (cytogenetic analysis) in blood cancer cells. FISH helps identify genetic abnormalities that may not be evident with an examination of cells under a microscope. This helps ensure that your child receives the proper treatment. Once treatment begins, doctors use FISH—usually every three to six months—to determine whether a therapy is working.
- Immunohistochemistry: A laboratory method that uses antibodies to check for certain antigens (markers) in a sample of tissue. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to the antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope. Immunohistochemistry is used to help diagnose diseases, such as cancer. It may also be used to help tell the difference between different types of cancer.
- Next-generation sequencing (NGS): The term “next-generation sequencing (NGS)” is a catch-all term used to describe a number of different modern sequencing technologies. These technologies allow for sequencing of DNA and ribonucleic acid (RNA) much more quickly and cheaply than the previously used sequencing methods. Consult your child’s doctor to discuss the possibility of next-generation sequencing as part of your child’s care. Next-generation sequencing is commonly used for patients with cancers that can be treated with targeted therapy.
Some doctors may recommend next-generation sequencing for patients with advanced cancer that is not responding to standard treatment. This approach may help doctors to identify other treatments that may be effective given the cancer’s genetic makeup.
- Polymerase Chain Reaction (PCR): A PCR is an extra-sensitive test that measures the presence of certain biomarkers in blood or bone marrow cells. It measures any remaining blood cancer cells not found by cytogenetic methods such as FISH. PCR is used to diagnose and check a patient's molecular response to treatment. It can also detect a specific DNA abnormality or marker found in patients with certain blood cancers such as acute promyelocytic leukemia (APL) and chronic myeloid leukemia (CML). PCR allows more sensitive follow-up of patients in remission and can help determine whether additional treatment is needed.
A white cell differential (also called a CBC plus differential, a differential, or a “diff”) measures the amount of the different kinds of white blood cells (leukocytes) in the blood. A white cell differential is often included as part of the CBC. This helps determine the body's ability to react to and fight infection. It can also identify various types and stages of blood cancers, detect the existence and severity of infections, and measure your child’s response to chemotherapy. The absolute neutrophil count (ANC) is the number of neutrophils (another type of white cell) in the blood that fight infection.
A white cell (WBC) differential also checks whether white cells appear normal. The types of white cells and the approximate percentage they make up in the blood are:
- Neutrophils (55% to 70%)
- Band neutrophils (0% to 3%)
- Lymphocytes (20% to 40%)
- Monocytes (2% to 8%)
- Eosinophils (1% to 4%)
- Basophils (0.5% to 1%)
Until children are more than 4 years old, they have a higher percentage of lymphocytes in their blood than adults do.
How is a white cell differential done?
After your child’s blood is drawn, it's placed on a stained blood slide and examined. The pathologist determines the percentage of different types of white cells present.
What do the results mean?
Abnormal patterns of white cells may point to infections, leukemia, immune disorders, inflammation, and other problems.
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Urinalysis
A urine test, also called a urinalysis, measures levels of proteins, blood cells, and chemicals in your child’s urine. This test can provide information about how their body is functioning and is often used to help diagnose kidney and bladder infections and other diseases. Many substances in the blood can be detected in the urine because the kidneys filter blood and produce urine.
How is a urinalysis done?
After your child urinates into a sterile container, the sample is either tested in the doctor's office using chemically treated paper or sent to a laboratory for analysis.
What do the results mean?
High levels of calcium in urine may mean low blood calcium levels, which can contribute to weakness, loss of appetite, nausea, confusion, lethargy, and other symptoms. Abnormal proteins in the urine can indicate the presence of a disorder or disease.
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