The complete blood count or CBC is one most often suggested type of blood tests. It involves the determination of the developed components or cellular of blood. Such evaluations are generally done by specific machines which investigate the various constituents of blood in less than 60 seconds.
A major section of the complete blood count comprises of the values of the concentration of red blood cells, white blood cells and platelets present in the blood.
The complete blood count test
The complete blood count test is carried out by taking sample of a few milliliters of blood from an individual who has come for the test. It can be conducted in different types of settings, which include laboratories, a doctor’s office, hospitals, etc. An alcohol pad is used to wipe clean a section of the skin and then a needle is penetrated into a vein present on this part of cleansed skin. This vein is visualized on the skin by the lab agent. The blood is then drawn from the needle with the aid of a syringe or with a connection to a particular vacuumed vial where the blood gets accumulated. This sample of blood is then analyzed in a laboratory.
Normal CBC Values
The values of a complete blood count test will usually include the following:
Red blood cell count:
- The RBC or red blood cell count indicates the quantity of red blood cells that occurs in a volume of blood. There is a slight variation in the normal range values between laboratories, but it usually falls between 4.2 to 5.9 million cells per cubic millimeter (cmm). It can also be considered as the erythrocyte count and can be stated in international units like 4.2 to 5.9 x 1012 cells per liter
- Red blood cells are found in millions of numbers in the blood circulation of humans and are the most common type of cells present in the blood. They are larger than platelets but smaller than white blood cells. Here are the causes of low RBC
White blood cell count:
- The WBC or white blood cell count refers to the quantity of white blood cells that are found in a particular volume of blood. There is slight variation in the normal range values between laboratories, but it is usually between 4,300 and 10,800 cells/cmm. It can also be considered as the leukocyte count and can be stated in international units like 4.3 to 10.8 x 109 cells per liter
- The white blood differential count: The WBC count consists of many different types which are divided or differentiated as per their shape and size. The cells that can be observed in a WBC differential count include lymphocytes, granulocytes, monocytes, basophils and eosinophils.
- When a machine is used to generate the percentage of the various types of WBCs, then it is referred to as the automated WBC differential. These white blood cell constituents can also be calculated on a glass slide that is placed under a microscope and by a trained laboratory agent or a physician. Such a process of counting the components of WBCs is known as the manual WBC differential. Here are the causes of low white blood corpuscles count.
Hematocrit or Hct:
- Hematocrit refers to the ratio of the volume of red blood cells to the volume of the total blood. The hematocrit normal range varies between the genders and is about 37 percent to 48 percent in women, and 45 percent to 52 percent for men. The hematocrit values are usually determined by spinning down a blood sample in a test tube, which results in the accumulation of red blood cells at the bottom of the test tube.
Hemoglobin or Hb:
- It refers to the quantity of hemoglobin in a specific volume of blood. Hemoglobin refers to the protein molecule found inside the red blood cells which the red color to the blood and supplies oxygen. The hemoglobin normal range differs between the genders and is about 12 to 16 grams per deciliter for women and 13 to 18 for men. In international units it is expressed as 7.4 to 9.9 millimoles/liter for women and 8.1 to 11.2 for men.
Mean corpuscular volume or MCV:
- It is the average volume of an RBC. This is a measured value that is derived from the red blood cell and hematocrit count. The normal range may vary between 80 to 100 femtoliters, which is a tiny proportion of one millionth of a liter.
Mean Corpuscular Hemoglobin Concentration or MCHC:
- It is the average hemoglobin concentration within a given volume of RBCs. It is a measured volume derived from the hematocrit and hemoglobin calculation. The normal range falls between 32 percent and 36 percent
Mean Corpuscular Hemoglobin or MCH:
- It is the average quantity of hemoglobin in the average RBC. It is a measured value derived from the red blood cell count and hemoglobin calculation. The normal range varies between 27 to 32 picograms
Red Cell Distribution Width or RDW:
- It is a calculation of the variability of the shape and size of red blood cells. A higher number signifies a greater deviation in size. The normal range falls between 11 and 15
- It refers to the quantity of platelets in a particular volume of blood. Platelets are not whole cells, but instead are pieces of cytoplasm from a cell present in a bone marrow known as a megakaryocyte. Cytoplasm refers to that portion of a cell without the body or the nucleus of the cell. Platelets play an important role in blood coagulation. There is a slight variation in the normal range values between laboratories, but typically falls in the range between 150,000 to 400,000/ cmm, which can be stated in international units as 150 to 400 x 109/liter
Mean Platelet Volume or MPV:
- It refers to average platelet size in a specific volume of blood. Here is more information on Mean Platelet Volume.
Use of a complete blood count test
A doctor may prescribe a complete blood count test to aid the diagnosis of a suspected condition as well as to evaluate the existing symptoms.
- For example, a low hemoglobin or RBC count may indicate presence of anemia, while their high levels may point to occurrence of hypoxia or bone marrow disease, etc.
- A high WBC count may point to the presence of an infection or a malignancy, while its low count may result from intake of certain drugs like chemotherapy medications or from bone marrow abnormalities.
- A high platelet count can indicate extreme inflammation, while low platelet count can signify as being the cause of excessive bleeding or of other underlying disorders.