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CancerQuest > Introduction to Patient Information > Introduction to Cancer Detection and Diagnosis > Complete Blood Count (CBC)

Complete Blood Count (CBC)

This section contains information on blood, blood cells and common blood tests.  Topics covered include:

• Introduction to Blood and Blood Tests
• White Blood Cells
  
• Red Blood Cells
  
• Blood cell lineage
  

Introduction to Blood

Blood has been substance of great interest to humans throughout history and it was one of the elements in the 'Four Humors' theory of life developed by Hippocrates, known as the "Father of Medicine". Today there is a much greater understanding of blood; what it is, what it does, and where it comes from.

The average adult human has about 5.5 L (~185 fluid ounces; 1 gallon=128 ounces) of blood, made up of fluid (plasma) and cells. The plasma makes up ~55% of blood and it contains water (~90%), proteins, nutrients, hormones, chemicals, and waste products. Blood cells make up the other 45%. ⁽¹⁾ There are 3 main types of blood cells; white blood cells (WBCs) also called leukocytes ('leuko' comes from the Greek word for white and 'cyte' refers to cells); red blood cells (RBCs), also called erythrocytes; and platelets, also called thrombocytes. All blood cells are formed in the bone marrow from a mother cell called the pluripotential [pluripotent means having more than one possible outcome] stem cell (PSC). These special cells can develop into any of the 3 types of blood cells. (Note: when blood clots, the fluid that remains is called serum. Serum is plasma that no longer contains clotting factors.)

Blood Tests

Today, blood tests are some of the most common and useful screening and diagnostic tools used by doctors. These tests can give important information about how the body is functioning. Some blood tests detect/measure chemicals present in the blood. Others examine the blood cells; one form of this kind of test is called a complete blood count (CBC) and it provides information about the number, parts, shape, and structure of the different cell types found in blood.

The amount of each type of cell in the blood is one of the important indicators of overall health. If any cell type is not present in "normal amounts" there may be a cause for concern, but it does not always signify a serious condition. There are a variety of things that can cause an increase or decrease in blood cell counts, visit a health care professional if you are concerned.

References for this page:

1. Hematology: Basic Principles and Practice, 5th edition. Ronald Hoffman, MD, Bruce Furie, MD, Philip McGlave, MD, Leslie E. Silberstein, MD, Sanford J. Shattil, MD, Edward J. Benz, Jr., MD and Helen Heslop, MD, FRCPA, FRACP. Churchill Livingstone (2009), Philadelphia, PA .