Guide to a Complete Blood Count

Complete Blood Count (CBC) Platelets—fragments of cells in the blood that are necessary for the blood clotting. Blood clotting protects the body by preventing the loss of blood following blood vessel injury. This test measures the number of platelets in a small volume of blood. Platelet counts are useful in the evaluation of several hematologic disorders.

Hematocrit (Hct)—a test used with hemoglobin tests and a red cell count to calculate the percentage of red blood cells in whole blood. Hematocrit levels are useful in evaluations for anemia (a reduction in the number of circulating red blood cells), polycythemia (excessive red blood cells), and dehydration (excessive loss of body fluids or water).

Hemoglobin—the red oxygen-carrying pigment of red blood cells. Hemoglobin levels are useful in the evaluations for anemia, blood loss, hemolysis, polycythemia, and other conditions.

Mean Corpuscular Hemoglobin (MCH)—the weight of hemoglobin in the average red cell. MCH is important in the evaluation of anemia, iron deficiency, vitamin B12 deficiency, thalassemia (group of hereditary anemias occurring in populations bordering the Mediterranean and Southeast Asia), and spherocytosis (abnormal red cells in the blood).

Mean Corpuscular Hemoglobin Concentration (MCHC)—the average amount of hemoglobin in the average red blood cell. MCHC is elevated only in hereditary spherocytosis. Decreased MCHC levels are found in iron deficiency, anemia, thalassemia, and some hemoglobin disorders.

Mean Corpuscular Volume (MCV)—the actual size of the average red blood cell. MCV is important in the evaluation of anemia, iron deficiency, vitamin B12 deficiency, thalessemia, and spherocytosis.

Polymorphonuclear Neutro-phils—the major white blood cells in normal adult blood. These cells play an important role in the body's defense against bacteria. They can attack and destroy bacteria that enter the body. Abnormal levels are associated with infections, inflammatory disorders and blood diseases. Physical and emotional factors (heat, cold, shock, etc) can alter the count

Red Blood Count—reports the number of red blood cells found in a microliter of whole blood. It is used to detect anemia, polycythemia, and dehydration.

White Blood Countpart of the complete blood count, the WBC reports the number of white cells found in a microliter of whole blood. Used to determine infection or inflammation, WBCs help determine the need for further tests such as the WBC differential or bone marrow biopsy. A WBC is also used to monitor response to chemotherapy or radiation therapy.