Complete Blood Count (cont.)
Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What is the complete blood count test (CBC)?
- How is the complete blood count test (CBC) done?
- What are the components of the complete blood count (CBC)?
- What are values for a complete blood count (CBC)?
- What are the functions of the cells in a complete blood count (CBC)?
- What is the complete blood count (CBC) used for?
What are the components of the complete blood count (CBC)?
The complete blood count, or CBC, lists a number of many important values. Typically, it includes the following:
- White blood cell count (WBC or
leukocyte count)
- WBC differential count
- Red blood cell count (RBC or
erythrocyte count)
- Hematocrit (Hct)
- Hemoglobin (Hbg)
- Mean corpuscular volume (MCV)
- Mean corpuscular hemoglobin (MCH)
- Mean corpuscular hemoglobin
concentration (MCHC)
- Red cell distribution width (RDW)
- Platelet count
- Mean Platelet Volume (MPV)
What are values for a complete blood count (CBC)?
The values generally included are the following:
- White blood cell count (WBC) is the number of white blood cells in a volume
of blood. Normal range varies
slightly between laboratories but is generally between 4,300 and 10,800 cells
per cubic millimeter (cmm). This can also be referred to as the leukocyte count
and can be expressed in international units as 4.3 to 10.8 x 109 cells per
liter.
- White blood cell (WBC) differential count. White blood count is comprised of several different types that are differentiated, or distinguished, based on their size and shape. The cells in a differential count are granulocytes, lymphocytes, monocytes, eosinophils, and basophils.
A machine generated percentage of the different types of white blood cells is called the automated WBC differential. These components can also be counted under the microscope on a glass slide by a trained laboratory technician or a doctor and referred to as the manual WBC differential.
- Red cell count (RBC) signifies the number of red blood cells in a volume of blood. Normal range varies slightly between laboratories but is generally between 4.2 to 5.9 million cells/cmm. This can also be referred to as the erythrocyte count and can be expressed in international units as 4.2 to 5.9 x 1012 cells per liter.
Red blood cells are the most common cell type in blood and people have millions of them in their blood circulation. They are smaller than white blood cells, but larger than platelets.
- Hemoglobin (Hb). This is the amount of hemoglobin in a
volume of blood. Hemoglobin is the protein molecule within red blood cells that
carries oxygen
and gives blood its red color. Normal range for hemoglobin is different between
the sexes and is approximately 13 to 18 grams per deciliter for men and 12 to 16
for women (international units 8.1 to 11.2 millimoles/liter for men, 7.4 to 9.9
for women).
- Hematocrit (Hct). This is the ratio of the volume of
red cells to the
volume of whole blood. Normal range for hematocrit is different between the
sexes and is approximately 45% to 52% for men and 37% to 48% for women. This is
usually measured by spinning down a sample of blood in a test tube, which causes
the red blood cells to pack at the bottom of the tube.
- Mean corpuscular volume (MCV) is the average volume of a red blood cell.
This is a calculated value derived from the hematocrit and red cell count.
Normal range may fall between 80 to 100 femtoliters (a fraction of one millionth
of a liter).
- Mean Corpuscular Hemoglobin (MCH) is the average amount of hemoglobin in
the average red cell. This is a calculated value derived from the measurement of
hemoglobin and the red cell count. Normal range is 27 to 32 picograms.
- Mean Corpuscular Hemoglobin Concentration (MCHC) is the average
concentration of hemoglobin in a given volume of red cells. This is a calculated
volume derived from the hemoglobin measurement and the hematocrit. Normal range
is 32% to 36%.
- Red Cell Distribution Width (RDW) is a measurement of the
variability of red cell size and shape. Higher numbers indicate greater variation in size. Normal
range is 11 to 15.
- Platelet count. The number of platelets in a specified volume of blood.
Platelets are
not complete cells, but actually fragments of
cytoplasm (part of a cell without
its nucleus or the body of a cell) from a cell found in the
bone marrow called a
megakaryocyte.
Platelets play a vital role in blood clotting. Normal range
varies slightly between laboratories but is in the range of 150,000 to 400,000/ cmm (150
to 400 x 109/liter).
- Mean Platelet Volume (MPV). The average size of platelets in a volume of blood.
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