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Full Blood Count Test in Hematology: Uses & Results Interpretation

Instructor: Heidi Howerton

Heidi has written education material for a well known hospital's pediatric neurosurgery unit and has her Bachelor's of Science degree in nursing.

In this lesson we will define what a full blood count test is and learn what this laboratory test specifically covers. We will also examine when a full blood count test is ordered and discuss how the results of this test are interpreted.

Case Study

Sarah, a 60 year old female, has been healthy most of her life, but lately has been feeling extremely tired. She dislikes going to the doctor and doesn't understand why annual appointments are needed. After much prompting from her daughter, Sarah makes an appointment to have an annual physical with her primary care physician. During that visit Sarah's doctor orders a full blood count lab test. Sarah, who dislikes having blood work done even more than visiting the doctor, questions her doctor about why this test is so important. Her doctor replies by telling her that she would be surprised how many lives have been saved through a simple full blood count test.

Blood Test in Laboratory
Blood Test in Laboratory

Full Blood Count Test

A full blood count test in hematology is a blood test that is used to examine the cells of a person's body and evaluate a person's overall well-being. Another common name for a full blood count test is a complete blood count (CBC). A full blood count test measures the following cells in a person's body:

  • Platelets: help blood clot
  • Red blood cells: help carry oxygen throughout the body
  • White blood cells: help fight infection
  • Hematocrit: the amount of blood that is made up of red blood cells
  • Hemoglobin: a protein in red blood cells that helps carry oxygen throughout the body

A CBC can also measure the overall size of red blood cells and the amount of hemoglobin present in red blood cells.

Red Blood Cells
Red Blood Cells

Uses

A full blood count test is often ordered at annual doctor appointments or when a physician has a concern and is trying to identify the cause of a person's illness. Full blood count tests help identify diseases and illnesses such as inflammation, anemia, cancer, infections, autoimmune diseases, liver disease, vitamin deficiencies, and bone marrow failure.

In our story, Sarah's doctor explained the different cells that a CBC measures and why this blood draw is important. He told Sarah that a full blood count test might provide the clues he needs to fully evaluate and diagnose her high levels of fatigue.

Normal Results

The following are normal ranges for the full blood count test:

  • Platelets: 150,000 - 450,000/mcL
  • Red blood cells: normal male range 4.7 - 6.1 million cells/mcL, normal female range 4.2 to 5.4 million cells/mcL
  • White blood cells: 4,500 to 10,000 cells/mcL
  • Hematocrit: normal male range 40.7% to 50.3%, normal female range 36.1% to 44.3%
  • Hemoglobin: normal male range 13.8 to 17.2 gm/dL , normal female range 12.1 to 15.1 gm/dL

Results Interpretation

Abnormal CBC results may indicate that something in the body is not functioning as it ought. However, full blood count tests are not definitive diagnosis tests (meaning they do not indicate a final diagnosis). In a healthy person with no other symptoms other than an abnormal full blood count test result, the abnormal CBC is not always a cause of concern. For this reason, it is important that the results of every full blood count test are evaluated by a medical professional to determine if additional tests or treatment are necessary. Sometimes full blood count test results that fall outside of the normal value range indicate that something is wrong in a person's body.

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