Blood studies are tests that examine a patient’s blood, and are the most common tests done for cancer patients. The doctor will choose from a list of chemical studies to be performed in a laboratory on your blood sample.
Blood studies provide important clues about what’s going on inside your body and help doctors follow the course of a patient’s disease and select the right treatment dosage.
Blood can be drawn in a variety of ways, depending on your child’s situation. The most common method of drawing blood is via inserting a needle into a vein.
If only a small amount of blood is needed, the doctor may obtain the blood sample by simply pricking your child’s finger. Children undergoing chemotherapy may have a central venous line in place from which blood can be drawn.
The blood sample is placed on a glass laboratory slide to be examined under a microscope or in a test tube for analysis.
Supporting Your Child
Children respond differently to getting blood drawn; some of them like to know in advance if blood is going to be drawn while others will become overly anxious at the prospect. Some children prefer finger pricks, while others prefer their blood to be drawn from a vein. It is important to try to find ways to give your child some choices, such as which finger or arm should be used so that they feel they have some control over what happens to them – it will help keep their anxiety levels down.
If your child is anxious about needles, talk to a member of the treatment team. There are various ways in which your child can be helped through medical play or relaxation to relieve their anxiety:
- Ask that the person drawing the blood use EMLA to reduce discomfort
- Distract younger children from the needle
- Give older children choices to help them feel in control
- Holding your child’s other hand or arm can be very comforting for them
- Plan something fun after the blood is drawn; give a young child an award right after the test to create a positive association with blood tests
It is important that you understand your child’s preferences and how they react to blood being drawn in order to appropriately prepare them in a way that minimises their anxiety.
Peter Kuhn, PhD, biophysicist at Scripps Research, and Kelly Bethel, MD, pathologist at Scripps Health, speak about their work, published in the journal Physical Biology, on a new test to detect tumor cells in the bloodstream. In the first of three video clips, the scientists discuss the need for the new technology.
Types of Blood Studies
Complete Blood Count (CBC)
A complete blood count (CBC) is a test to thoroughly examine the blood and which gives a general picture of an individual’s health. A CBC measures the number of red cells, white cells (neutrophils, eosinophils, basophils, monocytes and lymphocytes) and platelets and levels of haemoglobin and haematocrit in your blood.
It is the most common test done for children with cancer because it informs doctors how current treatment is affecting the bone marrow where blood cells are made.
A CBC can identify when your child is ready for their next round of chemotherapy, if a transfusion is needed, or whether there is an increased risk for infection.
Blood can be drawn for a CBC in a variety of ways, depending on your child’s situation. The most common method of drawing blood is to insert a needle into a vein, but blood can also be taken from a central venous line (a tube inserted into a large vein during a period of treatment).
Common Information Reviewed in a CBC
White Blood Count (WBC) measures the number of white blood cells present in the peripheral blood (blood that circulates in the body). White blood cells help fight infection. Abnormal results could be a sign of infection, inflammation, cancer, bone marrow problems or other issues within the body.
Diff (Differential Count) refers to the distribution of the various types of white cells in the peripheral blood; the values are expressed in percentages. These values change frequently in response to what is happening in the body. Increases in particular types of white cells can be signs of temporary or chronic conditions.
Platelet Count refers to the number or quantity of platelets (the smallest type of blood cell) present in the blood. Platelets prevent bleeding by helping the blood clot. The platelet count can be used to monitor or diagnose diseases. Significant decreases in the platelet count could mean that someone is at risk for bleeding in any part of the body.
Haemoglobin refers to the substance found in red blood cells that carries oxygen to other tissues of the body. It is expressed as a percentage of total blood weight. High numbers could be the result of dehydration or problems with the kidneys. Low numbers indicate anaemia, which could be the result of blood loss, problems with bone marrow, malnutrition or other issues.
Haematocrit measures the percentage of red blood cells in a given volume of whole blood. High numbers could be the result of dehydration or problems with the kidneys. Low numbers indicate anaemia, which could be the result of blood loss, problems with bone marrow, malnutrition or other issues.
Retic (Reticulocyte Count) refers to the percentage of young, non-nucleated erythrocytes (red blood cells) present in peripheral blood. It helps doctors determine the rate at which red blood cells are being created within the bone marrow.
Blood Chemistry Studies (CMP or BMP)
Blood chemistry studies consist of a group of tests called “chemistry panels,” and provide information about how your child’s organs (such as liver and kidneys) are functioning. It is especially important to monitor organ function during cancer treatment.
Depending on the type of panel, these tests can measure:
Electrolyte balance (such as sodium or potassium)
Blood glucose (sugar)
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)
Vitamins (such as B12 or folate)
Blood can be drawn for blood chemistry studies in a variety of ways, depending on your child’s situation. The most common way to draw blood is to insert a needle into a vein. Blood can also be taken from a central venous line (a tube inserted into a large vein during a period of treatment).