In a CBC, the various types of blood cell are analyzed, using six different tests:
Red Blood Cell Count (RBC)
Hematocrit
Hemoglobin
White Blood Cell Count (WBC)
Differential Blood Count (Diff)
Platelet Count
What is a red blood cell count?
Red cells, the most common type of blood cell, are responsible for transporting oxygen throughout the body. A red blood cell count (RBC) is ordered to check whether the number of red cells in the blood is abnormally high or abnormally low.
The ranges for a normal red blood cell count are:
Adult Females: 4.2 to 5.4 million red cells per microliter (uL, a millionth of a liter) of blood
Adult Males: 4.7 to 6.1 million/uL
Abnormal RBC may indicate:
Anemia (low RBC)
Polycythemia (high RBC)
What does hematocrit mean?
The hematocrit test, like the RBC, is performed to check whether the red cell count is abnormally high or low.
In the hematocrit test:
The patient's finger is pricked.
A drop of blood is drawn into a vary narrow glass tube.
The tube is spun at high speed (in an instrument called a "centrifuge").
The dense red blood cells pack down to the bottom of the tube, leaving the liquid portion of the blood at the top of the tube.
The fraction of the tube occupied by the packed red blood cells represents the fraction of red cells in the blood.
The ranges for a normal hematocrit are:
Females: 0.37 to 0.47 (37% to 47% of blood volume occupied by red cells)
Males: 0.42 to 0.52
Like an abnormal RBC, an abnormal hematocrit may indicate:
Anemia (low hematocrit)
Polycythemia (high hematocrit)
What is hemoglobin?
Hemoglobin, a compound present in red blood cells, gives blood its red color.
The molecular structure of hemoglobin allows hemoglobin to bind with oxygen (within the red blood cell). Circulation of red cells then serves to transport oxygen throughout the body.
The hemoglobin test, a measurement of hemoglobin levels in the blood, is another way of determining whether red cells are normal. Most patients with low hemoglobin also have:
Low RBC
Low Hematocrit
Normal ranges for hemoglobin are:
Adult Females: 12 to 16 grams of hemoglobin per deciliter (dL, a tenth of a liter) of blood
Adults Males: 14 to 18 g/dL
Low hemoglobin, like low RBC or low hematocrit, is an indicator of anemia.
What is a white blood cell count?
White blood cells are cells of the immune system, responsible for protecting the body from infection and malignancy. A white blood cell count (WBC) is ordered to check whether the number of white cells in the blood is abnormally high or abnormally low.
Patients with a low WBC are at increased risk for infectious disease.
Normal WBC count is 4.8 to 10.8 thousand WBC per microliter of blood.
Low WBC may indicate:
Overwhelming Infection
AIDS
Certain Cancers
Treatment for Cancer (either radiation or chemotherapy)
High WBC may indicate:
Infection
Leukemia
What is a differential blood count?
In a differential blood count (Diff), the numbers of different types of white blood cell are measured, to aid in a variety of diagnoses.
There are 5 different types of white blood cell:
Neutrophils: 3150 to 6200 neutrophils per microliter of blood
Lymphocytes: 1500 to 3000/uL
Monocytes: 300 to 500/uL
Eosinophils: 50 to 250/uL
Basophils: 15 to 50/uL
High neutrophil count can indicate:
Infection
Certain Types of Cancer
Arthritis
Physical Stress to the body, such as following:
Surgery
Trauma
Heart Attack
Low lymphocyte count can be a symptom of AIDS.
High monocyte count can indicate infection, often bacterial infection.
High eosinophil count can indicate:
Allergies
Certain Skin Diseases
Parasitic Infection
Immature white blood cells of any type can indicate:
Bacterial Infection
Leukemia
What is a platelet count?
Platelets are cell fragments essential for the process of blood clotting.
A platelet count may be performed if a patient:
Is Prone to Bruising
Is About to Undergo Surgery
A normal platelet count is 150,000 to 450,000 platelets per microliter of blood.
Low platelet counts ("thrombocytopenia") may occur as a result of:
Cancer Treatment
Certain Leukemias
Other Types of Cancer
Immune Thrombocytopenic Purpura
The material in this article is provided for informational purposes only. For specific medical advice or diagnosis, consult a healthcare provider.
