The hemogram or complete blood count (CBC) is used as a broad screening test to check for such disorders as anemia, infection, and many other diseases. It is actually a profile of tests that examines different parts of the blood and includes the following:
- Hematocrit measures the percentage of red blood cells in a given volume of whole blood.
- Hemoglobin measures the amount of oxygen-carrying protein in the blood.
- Mean Corpuscular Volume (MCV) is a measurement of the average size of your red blood cells. The MCV is elevated when your red blood cells are larger than normal (macrocytic), for example in anemia caused by vitamin B12 deficiency. When the MCV is decreased, your red blood cells are smaller than normal (microcytic) as is seen in iron deficiency anemia or thalassemias.
- Mean Corpuscular Hemoglobin (MCH) is a calculation of the average amount of oxygen-carrying hemoglobin inside a red blood cell. Macrocytic red blood cells are large so they tend to have a higher MCH, while microcytic red blood cells would have a lower value.
- Mean Corpuscular Hemoglobin Concentration (MCHC) is a calculation of the average concentration of hemoglobin inside a red cell. Decreased MCHC values (hypochromia) are seen in conditions where the hemoglobin is abnormally diluted inside the red cells, such as in iron deficiency anemia and in thalassemia. Increased MCHC values (hyperchromia) are seen in conditions where the hemoglobin is abnormally concentrated inside the red cells, such as in burn patients and hereditary spherocytosis, a relatively rare congenital disorder.
- Platelet Count is the number of platelets in a given volume of blood. Both increases and decreases can point to abnormal conditions of excess bleeding or clotting.
- Red Cell Distribution Width (RDW) is a calculation of the variation in the size of your red blood cells. In some anemias, such as pernicious anemia, the amount of variation (anisocytosis) in red blood cell size (along with variation in shape – poikilocytosis) causes an increase in the RDW.
- Red Blood Cell (RBC) Count is a count of the actual number of red blood cells per volume of blood. Both increases and decreases can point to abnormal conditions.
- White Blood Cell (WBC) Count is a count of the actual number of white blood cells per volume of blood. Both increases and decreases can be significant.