Appendix C: The Complete Blood Count (CBC)

The CBC test is used as a common screening test to check for a variety of disorders such as infection, anemia, and a wide variety of other diseases. It consists of a panel of tests that examines different parts of the blood and includes the following:

A. White blood cell (WBC) count: This is a count of the actual number of white blood cells per μL of blood. Both decreases in the total WBC count (leukopenia) and increases in the total WBC count (leukocytosis) can be significant. The normal range of WBCs ml of blood in both males and females is typically between 4500 and 10,000.

1. Leukocytosis is often seen during infections, inflammation, cancer, and leukemia.

2. Leukopenia is often seen during certain autoimmune conditions, bone marrow failure some severe infections, and congenital marrow aplasia where the marrow doesn't develop normally.


B. White blood cell differential count: This determines the number of each type of leukocyte calculated as a percentage of the total number of leukocytes. There are five different types of white blood cells: neutrophils, basophils, eosinophils, monocytes, and lymphocytes. An increase or a decrease in any of the types of WBCs can be significant.

C. Red blood cell (RBC): This is a count of the actual number of red blood cells (erythrocytes) per ml of blood. Normal levels are 4.5 – 5.5 X 106 cells per ml in males and 4.0 – 4.9 X 106 per ml in females. Both decreases in the total RBC count (erythropenia) and increases in the total RBC count (erythrocytosis) can be significant.

1. Erythropenia is seen in the case of anemia.

2. Erythrocytosis is seen when too many RBCs are being made or when conditions such as diarrhea, dehydration, or burns cause excessive bodily fluid loss.


D. Hemoglobin: This test measures the amount of the oxygen-carrying protein hemoglobin in the blood. Hemoglobin levels mirror the RBC count results. Normal levels in males are between 13.5 and 16.5 grams per deciliter (g/dL) and between 12.0 and 15.0 g/dL in females.


J. Mean corpuscular hemoglobin concentration (MCHC): This is a calculation of the average concentration of hemoglobin inside a red blood cell. Normal MCHC is between 31% and 37%. In disorders such as such as in iron deficiency anemia where the hemoglobin is abnormally diluted inside the RBCs, decreased MCHC values (hypochromia) are seen; in conditions where the hemoglobin is abnormally concentrated inside the RBCs, such as in burn patients, increased MCHC values (hyperchromia) are seen.


K. Red cell distribution width (RDW): This is a calculation of the variation in the size of the RBCs. Normal distribution width is 11 - 15. In certain anemias, such as pernicious anemia, the amount of variation in RBC size (anisocytosis) and variation in RBC shape (poikilocytosis) causes an increase in the RDW.


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Microbiology Laboratory Manual by Gary E. Kaiser, PhD, Professor of Microbiology
is licensed under a Creative Commons Attribution 4.0 International License.
Last updated: September, 2017