Complete Blood Count Test with Differential in Children
What is a complete blood count test with differential?
A complete blood count (CBC) test with differential measures the number and types of white blood cells in the blood.
Blood cells have important jobs. The body has 3 main types:
Red blood cells that carry oxygen through the body
White blood cells that help fight infection and disease
Platelets that help form blood clots after injury
A CBC test measures many aspects of the blood. A CBC with differential gives more details about white blood cells.
Blood contains blood cells and a liquid called plasma, made of water and proteins.
Children with infections, cancers, or blood disorders have changes in the number and kind of cells and proteins in their blood. Therapies and medicines can also change their blood.
Benefits of a CBC with differential
Health care providers use the CBC with differential to:
Diagnose a medical problem
Check if your child has an infection
Tell how your child fights infection
Study how a disease affects their body
Tell if a treatment is working
Getting ready for a CBC test
Follow your health care team’s instructions before the test. Tell them if your child is taking any:
Medicines (both prescribed and those without prescription)
These things may change the test results.
If your child is only getting a CBC test, they might be able to eat and drink as normal. But they might not if your care team orders other blood tests.
Steps of a CBC test
A care team member inserts a needle into your child’s vein to get a blood sample. They collect it in vials or tubes. The care team can also get blood from your child’s central venous access device such as a:
If your child does not have a device, the care team might start a peripheral IV to get blood samples.
Lab staff will study your child’s blood and report the results to your doctor.
What a CBC test measures
A CBC test measures:
Red blood cells (RBCs) – The numbers, size, and types of red blood cells
White blood cells (WBCs) – The numbers and types of white blood cells. The normal white blood cell count in healthy people is 5,000 to 10,000/mm3.
Platelets – The numbers and size of the platelets. A normal platelet count in healthy people is 150,000 to 400,000/mm3.
Hemoglobin – An iron-rich protein in red blood cells that carries oxygen to the body’s tissues. A normal hemoglobin level in healthy people is 12 g/dL.
Hematocrit (HCT or PCV) – How much space red blood cells take up in the blood compared to plasma and other cells
Reticulocyte count – The number of young red blood cells in the blood
Mean corpuscular volume (MCV) – The average size of red blood cells
The number of cells, their size, and types in a healthy person usually falls within a range of numbers (reference range or standard range). Your doctor compares your child’s results to these ranges.
Normal ranges can vary. They depend on your child’s age. Review these results with your care team. They can explain what is normal for your child.
What a CBC with differential measures
A CBC with differential includes more information about your child’s white blood cells.
Types of white blood cells
Neutrophils are the most common type of white blood cell. They fight off infection. Your care team may order an absolute neutrophil count (ANC) test to track your child’s neutrophil levels. When the ANC is below 500/mm3, the risk of infection is high.
There are 2 main types of lymphocytes: B cells and T cells.
B cells fight off invading viruses, bacteria, and toxins. B cells also play a role in the response to cancer.
T cells target and destroy cancer cells or cells infected with viruses.
Some types of cancer have abnormal B cells or T cells.
These cells remove foreign material such as germs and dead cells. They boost the body's immune response by making substances that fight disease.
These cells fight infection, inflammation, and allergic reactions such as asthma attacks. They also defend the body against parasites, bacteria, and fungus.
These cells affect allergic reactions, protection against parasites, and the immune response to some cancers.
Types of blood cells and related conditions
Low numbers or abnormalities of certain types of blood cells can lead to health conditions that require treatment such as: